You can make a reservation online - click on "Make a Reservation" (it's in the upper left corner of the page). You must make a reservation for the Fantasmic Dining Package specifically - just making an ADR at one of the three restaurants won't work. When you are inputting the desired date, time, party size, it should say "Fantasmic Dinner Package" under the "Select An Event". You will be asked for a credit card to guarantee the reservation.