What I did was install the material to the inside of the door outer sheetmetal , inside the door cavity(working through the large areas where the speaker was, as well as the large opening where the window regulators go in. )
Then, I did a layer on the back side of the door panel while it was off on the bench.
Then did a few extra layers in the immediate area of the speaker mounting baffle area, and any areas I thought it would seem helpful over the white plastic liner.
It takes time to clean everything thoroughly to ensure proper adhesion, and make sure everything is dry. then really take your time to set in nice, using the small roller that ususally comes with the kit, and working it with your hands. Be sure not to put it in places where there is a tight fit between mounting points or where you need to access clips or screws in the future. Some places you need to use smaller pieces to get the contour of the door correct, rather than simply slapping a large piece over everything. Also be cautious of moving parts like door lock mechanisms and door handle latch extensions.
Yes, I will probably get flamed for adding all the extra weight, as I also did a triple layer on the entire floor and up through the front firewall...but I never track the car anyway, so a few extra pounds is inconsequential to me.
Don't have a lot of good pics, but here are a few.
Curtis