Use a JIS #00 screwdriver to loosen the four screws along the top of the back cover. These screws stay in the cover after loosing them.

JIS (Japanese Industrial Standards) screws are not the same as Phillips. To avoid stripping these screws, make sure you are using a JIS #00 screwdriver and not a PHILLIPS #00 screwdriver. You can use a PHILLIPS #00 with a lot of downwards force but be warned this will deform the screw head and you risk stripping it.

iFixit's Phillips head screwdriver is designed to reduce damage on JIS head screws so it should be fine to use, still apply more force. Make sure it's iFixit's official Phillips screwdriver as we are unaware of any other manufacturer who does this.