Application is easy, just clean the existing sill with the included alcohol wipe, and take a practice run before removing the backing. Once you're comfortable with the positioning, remove the backing (avoid touching the sticky side), and position it over the existing sill, allowing it to gently lay down. Double check the position, adjusting as necessary, and then finalize by applying even pressure along the length of the sill protector
Should you ever need to remove it in the future, just apply moderate heat using a heat gun or hair dryer to soften the adhesive, and slowly peel it away. Any residue can be removed with Rapid Remover, GooGone or something similar.