Unless things have changed since we were there in August, you purchase the tickets at the guest relations window, which is to the left of the entrance turnstiles. (Not sure how this is affected by the DCA.)
We got in line shortly after 6:30 am on a morning when the park opened at 9. The window opened at 8 am (it opens an hour before the park). We weren't even able to get into the first showing. They allow people in line to purchase as many tickets as they want, so the short line may be misleading. It was 15 people per show, I believe, and we were 2nd to last to get seats.
Get there early or you may not get them at all!
DVC 12/00
WDW - 12/00 (DxL), 8/96 (CR/GF)
DL - 8/00 (offsite), 11/99 (DLH), 8/98 (DLH), 8/97 (offsite), 12/96 (offsite), 6/94 (DLH), and numerous visits as a child...