Heat an iOpener and apply it to the phone's back glass panel for two minutes.
A hair dryer, heat gun, or hot plate may also be used, but be careful not to overheat the phone—the display and internal battery are both susceptible to heat damage.
When the glass is warm to the touch, apply a suction cup close to the edge.
Lift on the suction cup and insert an opening pick in the gap.
If your back glass is badly cracked, covering it with a layer of clear packing tape may allow the suction cup to adhere. Alternatively, very strong tape may be used instead of the suction cup. You can also superglue the suction cup to the broken screen.
If your replacement part did not come with a flash lens, you must transfer it from your old panel.
Use a spudger or your finger to firmly press on the lens from the outward-facing side (the side you can usually see on the phone) of the glass panel until it loosens from its recess.
Remove the lens and transfer it onto the back side of the replacement panel.
Make sure to orient the flash lens properly such that the fresnel rings are stacked vertically.