Once you have a KeyCode you log into your profile and click on the 'Register KeyCode' Link. Enter you KeyCode in the box provided and click 'Register'. This will then generate a 'token' for the AIModule to collect.
Yes, you just set the story NOT to be downloadable anymore. It will not remove the story from members’ computers who downloaded it prior to you disabling download, though.
Assuming you’re using a Microsoft OS, the process will go something like this: program files > Ariasink > AIMod > data > file folder of the author and double click > delete the files you wish.