The protective sheets on the adhesive blocks, extensions, and tape strips have a slight overhang that you can grab with tweezers. Otherwise, just pick at a corner with tweezers until the sheet starts to come up. Be careful to not separate the thin film adhesive while you pull up the sheet.

If you find that the tape strips are pulling off the adhesive film when you try to remove the sheet, you didn't press hard enough to stick the adhesive to the paper. Press on the tape strip for a few seconds and try to remove the sheet again.