Remove the 6 screws on the edge of the laptop using a screwdriver.
Remove the back casing being held on by the one single screw. First, lift the casing at the edge where the screw once was, then carefully lift at the rest of the edges to loosen the casing. Pull the casing towards the edge where the screw was.
Remove the battery by sliding the switch circled in the picture and pulling the battery out.