Installing custom stories on Linux

[Spelos]

Custom Stories directory is
~/.steam/steam/steamapps/common/Amnesia The Dark Descent/custom_stories
(at least that's what it is on Windows, but I imagine it should be the same)
In that folder you should put a folder of the custom story you downloaded.

Usually it's the folder with the name of the mod and has "extra_english.lang" and "custom_story_settings.cfg" in it.

Hope you find this helpful