You can call central reservations and add it. YOu just need to give them your flight information. I had to add DME after I booked my package b/c the system wasn't working that morning. I got everything about 3 weeks before the trip. Just make sure you check the vouchers to make sure they're accurate. Mine had the correct flight numbers/times, but the wrong airline. It wasn't a problem checking in, but I had to call to verify the return information the day before we checked out.