Remove the inner back cover by unscrewing all three T6 screws (circled in the picture) with a T6 Torx Screwdriver.

Pull the inner back cover from the bottom towards you and then from the top upwards.

The inner back cover can be difficult to remove. You may need to use a Plastic Opening Tool. Near the top of the phone, insert the plastic tool between the cover and the phone. Gently pry the cover off.