Yes it's not easy to get these films to the window, but it's not impossible. Taken Fenstermaß tailored foil carefully. (But I have the hardware store a 1cm strong Styropurplatte 1m x 0.5m worried me as an underlay, after, the film can safe cut.) Then neatly cleaned with window cleaner the window, then pulled off towards the film and the transport foil. (This is very thin, so I gently a small piece of transparent tape from one side adhered to a corner and then abgepiepelt with a fingernail to the other part of the film and then peeled off the transparent transfer film completely, of course, gently) Now with a small spray bottle 0,5 l , filled with distilled water and 4-8 drops of detergent, spray the side of the decorative sheet completely, of which I have taken off the transport foil, just moisten the window neatly, then, oriented film on the disk, so and then with a small plastic squeegee the water horizontal slide out of each of the center to the right and left. With paper kitchen towels wiped the excess water and OLE glued the film, the window is opaque and transmits light and looks beautiful.
That was my way to the window decoration film. There are many ways to find yours.