Remove 3 self-tapping screws which fasten the metal plate to plastic posts below. You will need a long screwdriver and it will help greatly if it's magnetic. The rear screw on the right also retains an earthing lead.

Remove a machine screw and its earthing lead.

Lift off the metal plate.

Note that on reassembly small holes or notches next to the screw holes have to locate in pegs before the metal plate will go fully home. Make sure none of the cables connecting to the main logic board are trapped underneath.