This guide will teach you how to get to and install the back case of the phone.
To separate the battery from the phone, use your thumb to push in the button as shown.
Keep the unlock button pressed as you slide the battery away from the button.
Pull the battery away from the phone.
Use a T6 Torx screwdriver to remove the highlighted screws.
Carefully pry apart the two pieces, laying the back case to the side.