Dee, you can read details about it here:
http://allearsnet.com/din/fantdin1.htm
Basically, you choose from 3 restaurants (Hollywood & Vine, Mama Melrose & Hollywood Brown Derby) and at the end of your meal they give you a voucher to enter the Fantasmic ampitheater 30 minutes before the show. You enter at the front of the park... not the regular entrance to the ampitheater. There is special seating area (not in the center) set aside for dinner package guests. You are pretty much guaranteed a seat in that area without arriving super early. You can enter as early as you wish though. We like it because we enter at the latest possible time and still have good seats. FYI... On the dining plan, the dinner package counts as one TS at H&V and MM and 2 at HBD. We've never tried HBD but like H&V a lot. We're going to try MM this time!