REPLACING iPHONE 4 BACK SCREEN!?

ok i ordered a replacement gl panel for my iphone 4. i dopped it and cracked the back gl. the replacement i ordered from China is just the gl piece, theres no way to put it on my iphone 4. Theres no groves for it to sit back into the phone or anything, its just the gl piece itself. The package came with a mini flat head screwdriver, a mini screwdriver, and a little tool that looks like its used to pry open something. Does anyone have any idea how do i put it on my phone