I put the panel back on for my computer. I'd imagine its optional but I did it just to be safe

The panel is put on by putting the panel in the ridge between the outside tabs(the ones used to release it) and the inside tabs (closest to the memory slot)

The panel is secured by pushing the outside tabs onto the panel (Picture 2)

To put on the bottom case, line it up using the hinge and the cutout for the hinge, then make sure the screws line up

Screw down the Phillips till they're tight be careful not to strip them.