I did the Papal audience in June. I ordered ahead like you. I chose to pick up a day ahead to avoid any lines on the day of the event. On my pickup day there was a line that had lower priority than the security line for St. Peter's. It took about 45 minutes. I was the first in line and soon many were behind me, including an Italian priest who tried to convince the security that he didn't have to wait in the line I was in. So, he maneuvered his way to the front and cut in front of me. All picked up the pass at the bronze door.
I am glad I got the pass a day ahead, so that I wasn't in a rush or late to get a good seat.
I suggest getting to the event early and picking a seat right behind a left to right aisle. I was there 1 hour before. The Pope rides by and people rush to the front of the north south aisles to see him. Someone tried to take my chair as i stood up, but I stopped him and I stood on it to get a good glimpse and a video. I got lucky and a baby was handed to him for a kiss. I was 1 row behind the aisle in an end seat.
Enjoy! The gathering was about 90 minutes long and it got warm the time I was there.