It's only available for Disney resort guests now and they should send you an email with a personal link something like 40 days before your stay. If they don't, then contact them via the Photopass site. We didn't get our email (quite a lot of people don't even if registered) so I contacted them with details of our booking and they sent us a code for the equivalent discount which was actually even better as I could have used it for anything on the Photopass site if I had decided not to order the CD.