Starting near either of the 4 corners of the device notice the seam of the case around the front of the device.

Begin using the opening tool with a moderate amount of force to wedge between the back case and the phone.

Gently move the tool around the edges towards each corner until the back is removed.

You will be able to hear the back casing pulling apart from the phone. Do not be alarmed, but work gently with the device.