To start, apply pressure downward on the plastic piece connected to the usb port as shown. While applying the downward pressure, apply pressure away from the USB port as well.

You want to pull the plastic piece away from the bottom of the phone.

Once you have one side clearly separated from the shell of the phone, put the screwdriver in the opening you have created and push the whole piece away from its shell.

Completely remove the plastic piece from the back panel shell.