First, clean the window of the car to make sure there isn't any dirt or grime on the window where you'll be putting the decal.
Hold up the vinyl tint to the window and mark with something removable (ie.chalk or washable marker) so you can see where the vinyl is supposed to sit on the window.
Peel away the back of the paper on the top right hand corner. Slowly peel the backing off with your right hand while using a buffing cloth in your left hand to buff out any air bubbles that might be there.
After you're finished applying the vinyl, let it sit. You don't want it to shift or slide around before it's set.