You would call Member Services. The number will be n the documentation you receive from RCI re the trade. It's the same number you call to pay the additional fee exchangers pay Disney.
You can also arrange for Magical Express with Member Services if you plan to take advantage of that service.
Keep in mind that you must get the dining plan for very night of your exchange for every member of your party, even if you aren't arriving on the first night or staying the entire week You pay for the dining plan in full when you check in.