You are about to remove the button covers for the input buttons. You will find that it is separate from the rest of the buttons on the outside. There are a couple of screws that hold it in. Remove those.

There is another cover for the volume area that is held in by two screws. Remove that cover.

There is one more screw that is nearby it. It is to the right, and is closest to the edge of the unit next to the volume knob. This screw is attaching a metal plate which you will have to remove in the next step. Go ahead and unscrew this.