Downloadable Content for the PlayStation 3?

So I was looking at the downloadable content for the PS3 and I found the Marvel Ultimate Alliance 2 character add-ons back. So I downloaded the one where you can get Magneto, Psylocke, Cable, and Carnage, but when I started up my game and when I tried to switch those characters to my team, they were not there. Can someone please tell me how to fix this and how to active the downloadable content? I downloaded the disc based content and I am trying to use it on a disc based game. Thank you for your time.