Hey Schnake,
I was in the exact same situation for my Accurate Miniatures IL2m3 kit. The control panel decal is meant to be placed behind the control panel with the non sticky side on the bare clear plastic so that it shows through the dials of the control panel. The instructions said to remove the decal and flip it over so that the side facing up is now facing down onto the blue decal sheet that it came on. Move around the decal to get the adhesive onto the upward face of the decal. The instructions mentioned that this helps get the sticky or adhesive substance on the decal sheet to go onto the other side of the decal (that was originaly facing up). Then you can go ahead and put the decal on the winshield car and brush on a coat of gloss/dull coat (or future).
You can also brush some Micro Set (blue bottle) onto the clear windshield to help the decal adhere even more to the windshield.
Goodluck,
Kien