1. Go to BR's local file which can be found easily via your library to view local file, next do the same with Darkest Dungeon or any other game.

2. From the second window explorer that open up when you hit view local file from Darkest Dungeon, in the address bar go back to the steamapps (C:\Program Files (x86)\Steam\steamapps)

3. Open up the (workshop) folder > (content) folder > (262060) folder which is the darkest dungeon ID > ???

4. Once you enter, there is a bunch of numbered folders which are the various steam workshop for darkest dungeon mod ID, to figure out which mod is what, you can just view the mods you have subscribed to on the darkest dungeon workshop. Go to said mod page, right click to copy the page link, and paste it in your browser so you can find the mod ID in the url. Use that number to find which folder it is that you wanna use in BR.

5. After finding the mod you want, copy the folder, and go back into the BR window explorer that you open back at step 1. Inside there is a bunch of named folders, just look for the one listed as (mods)

6. Once you enter the mods folder, there should be a couple of others that came with BR, just paste it to the side somewhere. After you placed it, it is recommended to rename it to something you can keep track of such as this example: 884767042 - 3 trinket 3-30-23

Once done, enter your game, go to your save and enable the mod like normal Darkest Dungeon, Enjoy.

One last thing, most mods as BR devs said inside the game will not work, however some light UI mod should function more or less fine with just a few quirks such as expanded inventory that increases your slots, but BR adds a few item that is quite big and Expanded Inventory does not have those png readjusted to fit in the mod, so the BR item will take up more space visually. Do not use character mods unless the person who made it specifically says it work for BR.

Mods tested when I made this guide
884767042 - 3 trinket 3-30-23 ( https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=884767042 )
953207219 - Expanded Inventory 3-30-23 ( https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=953207219&searchtext=inventory )
2188081793 - All Skill Slot - 3-30-23 ( https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2188081793 )

In addition to what I said above about what mod would work. Any mods that include custom asset should in theory work. By custom assets, I am talking about abilities that has no tie to the Darkest Dungeon effects folder for abilities, so custom characters with custom effects asset should work just fine, but would need some tweaks using notepad++ or similar programs to double their damage output and health to be more inline with BR's way of balance. That said, if you are a casual, ignore this and stick to UI/Animation speed up mods, or until someone is kind enough to copy and paste existing mods at the permission of the original creators to make a BR version.

884767042 - 3 trinket 3-30-23 ( https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=884767042 )
953207219 - Expanded Inventory 3-30-23 ( https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=953207219&searchtext=inventory )
2188081793 - All Skill Slot - 3-30-23 ( https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2188081793 )
Faster combat ( https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1483754805 )
Level Restriction Removal ( https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=840391233 )
Endless Roster (999) ( https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1440253707&searchtext=999 ) works (when fully upgraded)