use soap and water to put the tint on the outside of the car, then use a squeegee <- (I fugged up the spelling) to get all the water out from under it, at the same time you need to use a heat gun to shrink it to the curve, don't expect to get it right on your first, or second try. cut it to the pattern of the window, then peel the backing off and put it on the inside, again with soap and water. good luck
I dont know where the baby powder thing came from, but that is NOT the correct way to do it disregard that.