Wedge the plastic opening tool in between the top and bottom cases. This may require a little or a lot of force so be careful.

Note: the phone should be face up and the plastic opening tool should be face downwards

Once you get the plastic opening tool in, slide it across the side of the phone, making sure to keep the plastic opening tool wedged in between the two casings.

Repeat the 3 steps above for the top, bottom, and opposite side.