I'm also confused about the plastic film. I removed the plastic film from the back of my new home button and the silver disk came off with it - the disk is not glued on to the home button. When I put the new button in place I tried as best I could to keep the disk in the same position it was in before I took the plastic off.

The new home button works OK (I only have to press 2x for it to respond) but it doesn't move at all when I press it.

Should I have left the plastic on? Is the little silver disk necessary? should i have glued the silver disk back on to the home button?

I want to go back and re-do it, but not until I have a better understanding of what to do.