Try using a spray bottle full of water with a few drops of liquid dish soap in it and sprits a little on the plastic then apply the sticker, position it where you want it and then squeegee out the water. Start at the center and work towards the edges, lightly at first then as it sets up do it harder until all of the water is out
Bondo spreaders works great, you might want to wrap it with a paper towel if it wants to scratch the sticker
Perfect placement with no air bubbles