Step 1: Open files and go Steam/steamapps/common/SourceFilmaker/game/workshop
Step 2: In that folder, click on models. Then click on robgamings
Step 3: go to frozty, then fnaf1
Step 4: Select all of the stuff in that folder and copy it
Step 5: Click the back arrow to go back to the robgamings folder
Step 6: Click on austinthebear, then go to fnaf1
Step 7: Paste in that folder
Step 7: Reload SFM and it should have worked

UPDATE 2025:
I downloaded SFM again and started browsing through the workshop, and I was surprised to have found an old discussion post that I made. Here are some common problems people have had, I'll try to answer them now.

No frozty folder:

I think you have to download the fnaf 2 map: https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1301764268&searchtext=fnaf

If that doesn't work, try the fnaf 3 map: https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1495428158

Arcade machines sideways:

To fix this, you must convert all of the entities into things you can animate. I don't know how to do this, and I'm sure there are other tutorials out there but I will at least try to help.

Step 1: Make sure draw game entities > other entities is enabled
Step 2: Press the record button
Step 3: Make sure camera position, camera angles, camera FOV, sounds, and view from player are disabled
Step 4: Hit record and wait until the sounds are done playing. Then press esc to stop recording
Step 5: Set draw game entities > other entities to disabled
Step 6: Click the + button in the top left, and select create animation sets for existing elements
Step 7: Select everything under models and click ok
Step 8: Delete "scout," and all of the weapons (starting with v_ or w_)
Step 9: Now you can rotate the arcade machines. Select the arcade machine, click on "static_prop - rot) and set the third number to -90