The elastic is looped over the bottom piece of the headgear and tied to the right size (tie the first time you put this on)

Put the mask on and then put the elastic band into the "slots" on both sides of the headgear - follow the pink arrow (tie it to size the first time) - each night I need to spend a minute or so adjusting it to feel best

It will then look in front like

and in back like







