Hi Lora! WOOT!!! Congrats on being able to score a reservation at Cinderella's Royal Table!! As I'm sure you are aware, Disney dining has implemented a cancelation fee policy pertaining to several of the dining experiences. When booking a reservation at Cinderella's Royal Table, your credit card will be charged in full. However, there are different circumstances when booking with a dining plan. Two (2) table service credits are redeemed for each person dining at CRT.
Being that you already have been charged for your dining experience, you need to call (407) WDW-DINE and alert them that you will be on the dining plan and would like to use your dining credits for that meal. They will be able to issue you a refund and note that you will be using the DDP at CRT. It does benefit you to do this prior to your stay, as it will take less time to sort it all out, and you will be aware of your DDP credits appropriately.
For future reference, when booking CRT or your other dining experiences that require pre-payment, head to the
Dining Reservations page of the
Walt Disney World website. There is a link that says "Use my dining plan to book pre-paid reservations". When this link it clicked, it will take you to a page where you are able to input your confirmation number as well as your arrival date. From there, you will be able to use you DDP to book your dining experiences.
Hope this helps you plan your magical vacation!
-Malanie