Originally Posted by KeeblerKO
Open the doors, grab the canvas door frame at the top, put your knee (or hip) into the LOWER door, and pull the top of the frame toward you. It'll bend it inward.
This is exactly right, I just added two words to clarify.
Bend it in so it's pretty tight - it should take a bit of effort to close, especially the first few times.
You can adjust most upper doors up and down by adjusting the little collars on the connection pins.