Clean the area thoroughly with rubbing alcohol or soap and water. Do not use Windex or similar products because it will leave a residue behind that will prevent the sticker from adhering well.
Measure and place the sticker in the desired location. Put a piece of masking tape down the center of the sticker to hold it in place.
Lift half of the sticker up and peel off the white paper backing. Hold the sticker taunt but be careful not to pull the masking tape off. Cut the paper backing off.
Slowly lower the sticker by rubbing it in place with a felt squeegee or a credit card wrapped in a sock. Start at the middle and then work your way out to the edges.
Fold the remaining half back and remove the paper backing. Slowly lower the sticker by rubbing it with the felt squeegee or sock covered credit card. Start at the middle and work to outer edges.