here’s how you’d add mods to longvinter:
find the path where your game is installed, it will look something like: G:\SteamLibrary\steamapps\common\Longvinter\Longvinter\Content\Paks
drag and drop the mods into that folder, as an alternative you can make a folder in there called “~mods” and put them in there
launch game and your mods should be ready 👍
(as an early access game constantly getting updated, mods could break if devs change the files with updates so keep that in mind)