Gotta pick up your tickets first, that's what you need to do by 5 p.m. You do that at guest services, which is just outside the gates. As you face the DL turnstiles, it's on the left. It's good to do this early or in the middle of the day when there's not much of a line.
At 7 p.m., one person in your party takes the tickets and checks in at the F! seating area. You choose your seats at this time. It's first come, first served, so people often line up around 6:15-6:30 so they can be first in line and choose front row seats. You'll find the check-in on Rivers of America, across from the Haunted Mansion, next to the churros cart. They usually pull out the podium around 6:30 and start checking people in right at 7.
Then you show up to be seated any time between 8:30 and the start of the show at 9. I'd suggest working your way over there around 8:30, because the area gets very jammed.
Have a great time!
