Start by placing the film with the backing paper on the surface (the grid system is facing the item and the sticky back plastic pattern is facing you). Make sure that you have an overhang on all edges. 

Gently peel away a small part of one corner and pull the backing paper slowly downwards. Now place the exposed sticky film on the surface. Don't forget to allow for the overhang. Use your squeegee to smoothen down the film. Start from the centre and work your way out to each side in order to avoid air bubbles. Now the sticky back plastic is stuck to a small part of the surface and won't glide around.

Now slowly pull the backing paper with one hand and whilst you smooth the film on to the surface with your cloth or squeegee. This is the tricky part so it pays off to take extra care. If you make a mistake you can easily remove the film and start all over again. The idea is to pull the backing paper as you go and only expose a small part of the sticky back at the time. This is to allow for a smooth and bubble free surface and to avoid the sticky back to stick to unwanted surfaces and tangle.

When you are happy with the result, use your sharp knife and gently cut off the overhang.