I have never gone for Christmastime before, so I feel like a WDW newbie again! Do I simply call and say I want the CP at such and such a restaurant for a certain date?
What's a CP? If it's the Crystal Palace...calling the dining reservation # and state what restaurant you want, for what date and what time you want to eat there, if they say it's booked ask for a ressie 10-15 minutes from the time you started with, or ask when can they accomodate the # of people in your party.
Candlelight Processional (the other CP ) dinner packages can be booked by calling the same number you call to make ADRs. The packages aren't available yet though. You can begin booking the package once the CP narrators for this year have been announced. This usually happens in late July or August. Once the narrators are announced, info about this year's dining package will be released.