You can call and book the Fantasmic Package through Disney dining. If you book either H&V, Mama Melrose, or Brown Derby, at the end of dinner they will give you a voucher to enter through a special 'package' entrance up till 30 minutes prior to the show. This means you don't have to wait in the regular line. The seats are to the right of the stage. They will not guarantee the seats afer 30 minutes and will release them to the general public.
You do not pay extra for the Fantasmic Package. You do have to give a CC when booking to hold the reservation. They will only charge your CC if you do not show up for the reservation and do not cancel.
I hope this helps!