So I purchased and installed Amnesia about a week ago from the Frictional site and now when i tried to run it, it asks me for a Serial Number! Where do I get a serial number from??
From the e-mail you got from them. If you have lost the e-mail, you can go here
https://shelf.frictionalgames.com/ and click on "Esellerate After Purchase Services" and type in your e-mail address under "Finding your order number."