So I bought a special edition of Prison Architect, but I don't know how to activate the code. Do I have to enter the code somewhere in the game? or somewhere else? I have the 'Prison Architect Name in Game Edition Key'. Does the key not work after a certain date?
If you are looking for the benefits that come with the "your name in the game" portion of your key, you need to follow the instructions in this link. Upshot is, you need to contact the developers and they will work your request.
Otherwise, your key is activated on Steam and has given you the game (and after a check of the product page, should have given you all of Introversion's other titles as well), and that should be all it does on Steam.