Custom Story File Help Please.

[Your Computer]

The installation for Amnesia, then, is likely to be C:\Program Files\Steam\steamapps\common\amnesia the dark descent\ if you're running a 32-bit Windows operating system; if you're on 64-bit, then the Program Files folder would be named "Program Files (x86)". You'll find the custom_stories folder in there. Let me know if you still can't find it or if you don't know how to reach the C:\ drive.