Choose a hard, smooth, clean surface on which you'll place your sticker.  Installing on your car's glass windows will work well.  Carefully peel off the thick, opaque paper backing.  The vinyl letters and outline should remain on the  lighter weight backing sheet.  Take your time peeling off the thick sheet -- the vinyl letter outlines in particular are very delicate. 
Put the sticker in place.  Rub your fingers over each letter and outline to assure a good adhesive bond.
Carefully peel off the remaining backer.
Enjoy!