How do you install custom stories and where do I download them? If it matters I own the disk version of the game so it uses a redist folder. I think that's what it was called.
You download the custom stories from either moddb.com, or from the Custom Stories section in this forum. Go into the Showcase. When you download them, it will be in a zip, most likely. Extract the folder into your redist > custom_stories folder, and you're good to go in-game.
I actually was introduced to the world of Amnesia mods through Desura.com, it's a software application similar to steam but based more on indie games and mods.
It helped me.