They need to be first collapsed from the correct direction. Try placing the box on a surface with the opening flaps facing up, then push one side down into the opposite corner (as shown in the illustration in the pop up instructions.) If it does not collapse well from the side you chose, try it from the adjacent side, & it should work.
For the large Igloo only, with the collapsed unit, it needs to be folded in 3rds just like our LiteDiscs. The illustration for this is at the very bottom of the instructions.
To make it easier to fold it, start with your hands in an opposite configuration on each side of the unit.
The best way I can think to illustrate this is to start with your left hand grabbing the left side of the folded igloo & turn the unit upside down by rotating the far edge upward and over [if you are doing this right, your left elbow will go up.]
Then grab the right side of the igloo with your right hand, so your right palm is on the opposite side of the unit as your left palm.
By twisting your arms/hands in this fashion it makes it easier to twist your hands back while holding the unit, to fold it into 3rds.
(see the illustration in the instructions for the visual)