With Mylar - to prevent bubbles. Hold the sheet up that you want to apply, lightly spray with a mix of water and a tiny dash of washing liquid - only needs to be light. apply the whole sheet to the pf and squeedgy out using a credit card or similar.
 OK - allk you lot in horror!!! AAAAAAAARRRRGGHHH!!!! WATER ON THE PF!!!!!!!
 Its not a problem - its only light spray and will do no harm.

To do the dry method, which in my opinion is a bigger risk. Leave the backing paper on. peel off the top 1"or so and lay this at the top of the PF. Run your credit card / old age pension bus pass whatever along the top to get it to really hold.
As you peel away the backing tape - have a straight edge run along the top of the mylar at the same time keeping it as close to the PF as possible - does this make sense?

 But mainly, as you peel away you must be applying at the same time.

There....bloody clear as mud