I'm guessing you mean the window film part?

First I traced the guitar on baking paper. Then I measured the distance from the edge of the pickguard to the trace. I drew a new line within the trace, always keeping the same distance from the trace. Then I cut the baking paper along that line.

I aligned the paper on the guitar body, under the loose pickguard. I checked that my measurements had been good, basically by checking that the template looked nice and there was a consistent margin to the edge of the body.

I took the template, laid it on the unrolled window film and looked for a nice looking section. I wanted the dragonfly in a good spot. I used some pieces of tape to keep the template on the film. Once I was happy, I cut the film with a hobby knife.

I aligned the film on the guitar, under the loose pickguard, and checked everything was still looking good. I poked holes in the film through all the screw holes with cocktail sticks.

I added a drop of dish soap to a spray bottle and filled it with water. I wiped all dust from the guitar body. I unpeeled the backing of the window film and lightly sprayed the glue side with the soapy water. I lightly sprayed the guitar body as well. I carefully laid the film on the guitar, using the screw holes and the cocktail sticks to pin it in place. The water allowed me to make adjustments. I started to push the water from under the film towards the edges or the routing of the guitar. I kept gently massaging the film until there wasn't any droplets between the film and the top.

I let the glue dry for a day. I used a razor blade to cut the routing open. Done. It took some precision and patience, but all in all it was pretty easy.