Arrive on time or a couple of minutes early. No more.
If you preorder you will walk up the left side of the bridge and to a cashier who will confirm your order and take payment.
Then you walk in and find a seat.
Only wait should be if there are guests in front of you at the cash register.
You SHOULD be able to go into the prorder link and view what you have ordered.
They will also confirm it and ask if you want to make any changes at the cash register.