Alan Wake's American Nightmare and the psychological horror game Observer are both free for a limited time on the Epic Games Store. These games normally cost 6.99 and 27.99 euro but for the next seven days you can get them for free. The offer ends on Thursday, October 24.
To get the games, just go to the Alan Wake's American Nightmare and Observer pages on the Epic Games Store, and click the "GET" button. Once you get the games, they will be yours forever.