you don't have to do anything @ 36 hrs. Any time AFTER 24 hrs, you can print your boarding passes (the letter/# will already have been assigned) in any way that's convenient for you. You can wait until you get to the airport if you want - makes no difference. We used it only returning home so we didn't have to interrupt our play time and our boarding passes were hanging on our door the morning we checked out so we literally had to do NOTHING!!
Hope this helps!