If you are booked on your POR reservation as a room only reservation, you will have to have it cancelled and changed to a ticketless room plus dining package for annual passholders. Unless it's a DVC reservation, the dining plan is only available with packages, so they've invented room plus dining packages without tickets, but if you want one of those it ceases being a room-only reservation. You will need to pay a new deposit of $200 (if you're within 45 days of arrival you will need to pay in full) and you won't be able to transfer any of your current deposit, which will be refunded.
What I do not know is if you can apply a Florida resident discount to a ticketless package for AP holders. I know an AP room discount can be applied.
WDW has recently made it possible for anyone to book a ticketless package, but if you're not AP or military you can't apply a room discount to a ticketless package at all, so you'd be better off doing it as an AP holder.
For a non-DVC reservation, you must add a dining plan no later than 72 hours before arrival, but if you're changing from room only to a package, you need to do that more than 5 days before arrival (6 if you booked online) to avoid cancellation penalties for the room only reservation.
For a DVC reservation, you must add a dining plan no later than 48 hours before arrival. If you are renting, you will need the DVC member to add the plan to the reservation for you, because Member Services will only deal with the actual member. It must be paid for when it is added, so you'll need to talk to the member about how you are going to supply the payment, since you can't call Member Services yourself. You cannot add a dining plan or pay for one at check-in.