Braces Owner's Manual - Using Headgear

Headgear is used to prevent forward growth of the upper jaw
 so that the lower jaw can catch up.
It also moves the molars back in the mouth to help create space.

Put both arms of the headgear into the mouth.
Put one arm into the headgear tube on the molar band on one side.

Make sure the arm is completely in the tube.

Now place the other arm in the other headgear tube.

The headgear strap should then be secured to the metal portion as instructed.