Please check the troubleshooting guides before posting!

[Romulator]

You need to extract all the files from the archive and place them in the folder Amnesia.exe is located. If you're on a Windows, it should be placed in here:

Steam: C:/Program Files (x86)/Steam/steamapps/Common/Amnesia - The Dark Descent/
Retail: C:/Proogram Files (x86)/Amnesia - The Dark Descent/redist

You also must use either the 1.3 or 1.2 Level Editor from here: https://wiki.frictionalgames.com/hpl2/tools/start

If you have a Steam copy, you should use 1.3. An up-to-date retail copy should also be 1.3.