Locate somewhere on the temple sides (i centered mine along the edge that runs from your cheek to your temple)

Take the pointy ring and press the pointy side into the cardboard from the inside of the goggles. you should just barely see the points sticking out.

Select the female snap parts and place it on the points, (the correct side will be the side with a slight folded lip around the outside (where the points are going to curl into) its more obvious on the male snap parts so compare them)

Crimp down pretty hard with your pliers, making sure they are well centered in the snap pliers. release and look to make sure the points all went inside the snap ring. and are not poking out and that the snap is now affixed well.

Repeat for the other side, and if you want a nice support sling over the top, put one in the middle of the velcro flap that holds your phone in, i put all female snaps on the cardboard, and male on the straps, makes it easier to swap and try other configs.