You don't need to do anything. They have it in their system that you are a
DVC member. They'll leave meet 'n greet info in your room. They were handing out the red DVC ball caps for current owners but you had to stop by the desk to get it. There were add on specials, but I don't recall any of them being good enough to jump on them. I believe there are better deals to be had on the member only cruise.
Have a fabulous Turkey Day cruise.