Turn the computer over and open it up.

Remove the following 14 screws:

Six 2.5 mm Phillips on either side of the keyboard area.

Five 4.5 mm Phillips on the left half of the keyboard area.

One 7 mm hex in the upper left corner of the upper case (a T6 Torx driver will do the job nicely).

One 15 mm Phillips in the upper middle of the keyboard area.

One 16.5 mm hex in the upper right of the upper case (again, a T6 Torx driver will work well).