Close the screen, and flip the computer over so that you can work from the bottom once again.

Notice the holes labeled with "F5".

Remove all screws in these holes.

NOTE: You may have to move the wireless antenna. Notice the track to the right of my finger that the wire is fed through. Be sure it is out of this track.

NOTE: There is a hidden screw on the outside of the slot where where you pulled the optical drive from, which is referenced for you in the 3rd picture.

There are 13 total screws.