Use a Phillips screwdriver to remove the six screws securing the back cover:

Four larger 6.6 mm-long black screws

Two smaller 4.8 mm-long silver screws

Despite the standards, Phillips screwdrivers can vary in size and shape—two drivers labeled as the same size may fit differently in the same screw. Use the size that fits the most snug into the screw head to avoid stripping it.