saves the roof from getting scratched

Decide the correct position of the roof light and wash the area. Anything still on the roof will be trapped under the roof saver
Spray the clean area with a soapy solution, ( cheap washing up liquid ) 4 or 5 drops to each litre of water

Peal off the backing paper, as you do this, spray the same soapy water on the sticky side.

If its windy, don't let the saver fold back on it self until the water is on. This stops it sticking on its self.

Place the saver on the roof, move it around to get it square.
Start in the middle and squeegee the water out. You can put the roof light on straight away.