Install is pretty strightforward. Wash and degrease the area really well, I love dawn dish soap for this, rinse it really well, then dry it down with a nice lint-free cloth. Now, measure from the same point on both sides and use a piece of masking tape (i like the blue stuff since it peels off nicer) to hold your decal in place. Get both sides even and taped in a few spots, make sure the decals are perfectly vertical, don't use bed lines for reference, they aren't parallel to the ground. Once it's aligned nicely, you can start peeling the backing off, sa you do this, have a silicone squeegee to push the decal onto the surface and to pull any air pockets. I like to start from the top and work down, but try to be as smooth about this as you can.
Here's a good video, it's onto glass, but same concept. I don't like windex, I prefer the soap; rubbing alcohol is the best though.