You can only add a dining plan to a package reservation so if you booked a regular room only reservation (and not through the DVC office) you will have to re-book with a package and cancel the room only. A new package deposit will be charged and your room only deposit will be refunded. If you have already purchased tickets you can book a ticketless package. It will follow all the rules of a package (e.g. deposit, final due date, penalties and change fees, cancellation rules) and can be booked only by calling.