The Steam version of FNaF: Secret of the Mimic has many achievements to unlock.
These are mostly simple and easy to get with a couple of exceptions of course.
That being said, feel completely free to try and get all of these achievements!
This guide also contains some SPOILERS for the game, you have been warned!

“Get jumpscared.”
Get jumpscared.

“Played party games with a Jackie in the Box.”
Survive Jackie's encounter.
This is an unmissable story related achievement.

“Boop the nose.”
Throw a ball at the nose in the Smack A Clown carnival game at Big Top Showroom.

“Knock out all the teeth in a single round of ball toss.”
Knock out all the teeth in the Smack A Clown carnival game at Big Top Showroom.

“Shoot a "threat" with a ball gun.”
Shoot Mr. Helpful with a ball gun at Big Top Showroom.

“Get high scores on all carnival games.”
Get high scores of 60+ (shooter) / 20+ (balls) on all 5 carnival games.
This achievement may be kinda bugged.
1. In Big Top Showroom (unmissable story carnival game).
2. In Big Top Showroom (unmissable story carnival game).
3. In Big Top Showroom (unmissable story carnival game).
4. In the Warehouse, complete the puzzle and enter the green trolley to find the carnival game.
5. In a Warehouse(?) room close to the Admin Entrance, when you go down an elevator after completing the second crane puzzle, go right. This carnival game requires saving one of the Big Top Showroom guns in the inventory system, as it doesn't give you a new one.

“Return from the Big Top Showroom.”
Survive Big Top's encounter.
This is an unmissable story related achievement.

“Teach the pirate crew a valuable lesson.”
Complete Captain Foxy's Puppet Show.
This is an unmissable story related achievement.

“Complete all repair tasks.”
Complete all 3 elevator repair tasks.
This is an unmissable story related achievement.

“Return from the Recycling Center.”
Survive Dollie's encounter.
This is an unmissable story related achievement.

“Enter the Storytime Showroom.”
To enter the Storytime Showroom, break all teeth in one round of the Smack A Clown carnival game at Big Top Showroom and then break only 4 in the next round to open up a path. Enter that path and continue until you reach the Storytime Showroom.

“Find the party room.”
Open the keypad locked door in the Admin Wing with the code 01350.

“Get executive access to the MCM.”
Get executive access to the MCM.
This is an unmissable story related achievement.

“Stay up your bedtime.”
Enter the Retail Showroom with executive access through the Welcome Lobby and open the keypad locked door with the code 80625, then finish the puzzle.

“Take a "shortcut" through the basement.”
Survive White Tiger's encounter.
This is an unmissable story related achievement.

“Run Edwin's "Parachute" program.”
Run "Parachute.exe" in the main terminal with executive access.

“Take a ride to the main house.”
Arrive to the main house after choosing to run "Parachute.exe".

“Keep the Data Diver and walk off the job.”
Get the Parachute(?) Ending.
To get the Parachute(?) Ending, run "Parachute.exe" in the main terminal with executive access.

“Hand over the Data Diver and leave the building. A job well done!”
Get the Normal(?) Ending.
To get the Normal(?) Ending, hand over the Data Diver when Dispatch asks for it.

“"You have found my presents. You have completed my tasks."”
Finish "MOON.exe" and take Glitched Permission.
To finish "MOON.exe", you need all 25 collectibles, one of them is only available in New Game+.

“Deposit every collectible into the inventory system.”
Deposit all 25 collectibles into the inventory system.
The game needs to autosave for the collectibles to register.
1. DEADEYE ROXY RODEO HAT
Next to a Retail Showroom door in the first security office area.

2. SHARPAY PLUSHIE
Right after getting past the first encounter with the Elephant.

3. HEDGEHOG MASK
In the security office where you get repair access.

4. FALL FEST SNOW GLOBE
In the room with Jackie's Box.

5. MONTY'S WATER GAME
Behind the pig in the Welcome Show room when you have to restart it.

6. PARTY TIME CHICA VACUUM CUP
On a vent in front of the first broken elevator after repairing it.

7. SWING BEE HONEY BOTTLE
In a secret path behind Jackie's Box after she's gone, you must enter the code 4782 in Birthday Showroom, which is next to Big Top Showroom. Proceed and then enter the code 0434 in another keypad locked door.

8. STAR ORPHAN NIGHT LIGHT
In Storytime Showroom after opening the staff door with the terminal.

9. GRAND PRIZE TROPHY
After winning the Big Top Showroom grand prize.

10. RANGER ARMY KNIFE
In a creator locked door next to the second collectible from this guide.

11. LIL' SEWING KIT
In a creator locked door in the keypad locked door before getting to the Manager's Office elevator, the code is 26294.

12. TOY PHONE
In a creator locked door in Birthday Showroom.

13. FREDBEAR PIZZA MAKER
In a creator locked door in the same place as the Big Top Showroom collectible.

14. PIRATE FOXY PUPPET
In a creator locked door in Storytime Showroom.

15. FREDBEAR SINGING RECORD
In a security locked door in front of the Theater projector room.

16. TOY HAMMER
In an admin locked door in the Workshop, behind a gate you can only open if you reach the Workshop through the Theater, past the projector room.

17. FALL FEST TICKET BOOK
Backtrack to the first crane puzzle, go through the admin locked door upstairs in the Theater area that connects with the crane puzzle. Now you need to lower the elevator closest to the path to the collectible, then go down the other elevator which should be up, and then go up the elevator you first lowered.

18. DAVID BLOCKS
In the Warehouse area with a green trolley that goes up and down whne you complete a connect puzzle, enter the trolley and then play a carnival game that has secret path behind it, you open it the same way you open Storytime Showroom.

19. JUNIOR DOCTOR'S KIT
In Loading Bay, the second crane puzzle room.

20. PET FISH NET
In an admin locked big door that says Welcome Show, this is left side after the second crane puzzle.

21. RAINY DAY BOOT
After beating Deadeye Roxy's carnival game, there's an achievement about carnival games in this guide so check it out to know more.

22. BIRTHDAY CAKE
In the office area with a bunch of cupcakes, enter the code 01350 in a keypad locked door.

23. DAVID'S TOY BALL
In an executive locked door that says Retail Showroom, this is in the area with a Clean-O-Vac statue and a bunch of mascot suits, the same are where you get the audio to repair the first elevator. In Retail Showroom, open a keypad locked door entering the code 80625, complete the puzzles and the collectible is yours.

24. VACUUM PET
In the main house, upstairs, you only get here if you choose to run "Parachute.exe".

25. WHITE TIGER DOLL
In New Game+, the collectible will be located in the first main security office.

“Listen to every Audio Log.”
Listen to all 22 audio logs.
The game needs to autosave for the audio logs to register.
1. Showroom Lobby, in a repair locked door.
2. Storytime Showroom, taking the elevator up, in the room where you open the staff door.
3. Roof Access, upstairs in the room where you get creator access.
4. Theater Stage Controls, next to the Projector Room.
5. Workshop, in the room with the springlock suit next to a terminal.
6. Backstage, that one area where you have the springlock suit, next to a terminal.
7. Returns, an admin locked door, in the Main Hallway next to the elevator that takes you to Manager's Office.
8. Loading Bay, the second crane puzzle room, right after entering it next to a terminal.
9. That hallway after beating the second crane puzzle, go right through an admin locked door.
10. After exiting the previously mentioned admin locked door, go forward and right through the door that goes to the Warehouse catwalks.
11. Admin Wing, in an admin locked door.
12. Executive Office.
13. Next to the elevator that takes you to Basement 2 after exiting the Executive Office through vents.
14. Basement 2, next to a terminal.
15. White Tiger's area, in a hidden room, after getting the second shining star (the sad one), go back hugging the left wall until you find a vent.
16. Research & Development, in an executive locked door next to a Springlock suit, you only get here if you choose to run "Parachute.exe".
17. Research & Development, in the Prototype Freddy's Pizzeria Bathrooms, you only get here if you choose to run "Parachute.exe".
18. Right before taking a ride to the main house, next to the cart ride, you only get here if you choose to run "Parachute.exe".
19. The Main House, in a room next to a vent.
20. The Main House, in a glitched locked door, you need Glitched Permission to enter it.
21. The Main House, in a glitched locked door, you need Glitched Permission to enter it.
22. The Main House, in Edwin's Destroyed Office.

“Collect all text logs.”
Collect all 61 text logs from the 42 mailboxes.
The game needs to autosave for the text logs to register.
1. MAIL - AUG 3RD
MCM outside at the start of the game, go left after exiting the van.

2. POWER
In the hallway leading to the main security office after the Welcome Show.

3. GROUP CHAT #1 + GROUP CHAT #2
Main Hallway, right after the first elephant encounter next to a collectible.

4. @#*$^%A
Welcome Lobby, on a vent in front of the first broken elevator after repairing it.

5. LOVE THAT TICKET BOOTH!
Showroom Lobby, right there where the reception desk is.

6. THEATRE - ONE MORE INJURY?
Theatre, in a security locked room in front of the projector room, next to a collectible.

7. SPELL CHECK + SPELLING IS FINE!
Workshop, the area where you have to find like 5 animatronic parts, it's there next to some standing and hanging suits in a long wide hallway.

8. SALES PITCH + SALES PITCH - REJECTED!
Workshop, upstairs in the little room where you lower the head animatronic part.

9. WE NEED TO GO
Workshop, downstairs in the little room where you grab the head animatronic part after lowering it.

10. VACATIONS
Workshop, right in front of one of the animatronic parts, you can spot this mail box through a gate when you enter the Workshop.

11. PROJECTOR ISSUES
Backstage, that one area where you have the springlock suit, next to a terminal and audio log.

12. MOVING ON!
Backstage, after crossing the bridge, behind the thing you use to go up with the springlock suit.

13. I CAN'T TAKE IT
Doll Hospital, when being hunted by Dollie, right after opening the first creator locked door.

14. ENERGY QUOTA
Doll Hospital, when being hunted by Dollie, in the room you get to through a vent, next to a terminal.

15. GROUP CHAT #5
Doll Hospital, when being hunted by Dollie, pretty much in the center of the area, next to a door only Dollie can open.

16. GROUP CHAT #4
Doll Hospital, in the room where you upgrade to admin permission.

17. RETURN LETTER (x4)
Returns, in an admin locked door, left side after exiting the bathrooms of the previous mailbox.

18. THEATER - ANYONE SEEN GARY?
Theatre Backstage, under the first crane puzzle, in an admin locked room. To get here after beating the section normally, go through the admin locked door upstairs in the Theater area that connects with the crane puzzle.

19. GROUP CHAT #3
Loading Bay, the room with the second crane puzzle, next to the controls for it.

20. CHICA'S PARTY WORLD
That hallway after beating the second crane puzzle, go right through an admin locked door.

21. *@#&^$&%
That hallway after beating the second crane puzzle, if you've gotten the previous mailbox, exit its room and go forward until you see it.

22. HAVE YOU HEARD FIONA?
In a room close to the Admin Entrance, same area where you play Deadeye Roxy's carnival game.

23. WASTE OF MONEY
Next to the big door that goes to Admin Wing.

24. ADMIN - DEC 1ST - 8:00 AM
Admin Wing, the cupcake room, go forward a little and it's there on the right side next to a locker.

25. ADMIN - DEC 6TH - 4:00 PM
Admin Wing, the cupcake room, literally next to the keypad locked door.

26. ADMIN - DEC 1ST - 12:00 PM + ADMIN - DEC 1ST - 12:15 PM + ADMIN - DEC 1ST - 12:30 PM
Admin Wing, the cupcake room, right side after getting the previous mailbox.

27. ADMIN - DEC 3RD - 3:05 PM + ADMIN - DEC 3RD - 3:20 PM
Admin Wing, the cupcake room, continue through the intended path and it's at the left side of the open hallway, in front of an admin locked door.

28. ADMIN - DEC 5TH - 5:00 AM
Admin Wing, the cupcake room, at the end of said open hallway in a small bathroom.

29. ADMIN - DEC 2ND - 4:13 AM + ADMIN - DEC 2ND - 4:18 AM
Admin Wing, the cupcake room, get out of that hallway through the intended path and go left.

30. ADMIN - DEC 4TH - 8:19 PM + ADMIN - DEC 4TH - 8:34 PM + ADMIN - DEC 4TH - 10:00 PM
Admin Wing, the cupcake room, same area as the previous one but go forward instead of left, past the stairs.

31. PLEASE ADVISE
Admin Wing, behind a Mrs. Helpful desk next to where you get executive permission.

32. @#$#*%^
Admin Wing, next to the vent that gets you to the executive permission.

33. STAFF CONTACTS
Admin Wing, in the room where you get executive permission.

34. 01010011 01000001 01000100 + 01101000 01110101 01110010 01110100
Executive Office.

35. LOCATORS
Basement 2, in front of a terminal and audio log.

36. SO BORED!
After exiting the White Tiger's area, in this hallway that gets you back to the main security office.

37. CONFIDENTIAL
In an executive locked door, in the bathrooms of the Main Hallway area next to the Manager's Office elevator, through a keypad locked door, the code is 26294.

38. RETAIL (x7)
Retail Showroom, you get there with executive access through the Welcome Lobby, next to the keypad locked door.

39. NIGHT SHIFT
Basement 1, in an office in the area after opening the Retail Showroom keypad locked door, the code is 80625.

40. SPRINGLOCKS
Research & Development, in the Fredbear room, you only get here if you choose to run "Parachute.exe".

41. 01001000 01001111 01001101 01000101
Right before taking a ride to the main house, it's hard to miss, you only get here if you choose to run "Parachute.exe".

42. RECEIVED: 5 MIN AGO
The Main House, next to a terminal after opening the keypad locked door.

“Fix what is broken.”
Get the Secret Ending.
This ending is only available in New Game+.
To get the Secret Ending, finish "MOON.exe" and take Glitched Permission, then run "Parachute.exe" in the main terminal with executive access. When you arrive to the main house, open the glitched locked doors to find the 6 Bedtime Story audio tapes, then take the White Tiger collectible to the vent that will open once you find every audio tape.

“Obtain all other achievements.”
Unlock every achievement above.