Install CDrom hardware

Front faces usually are of one of two types:

* small "fingers" with "barbs" (like the tip of a barbed fish-hook, or like a piece of Velcro) that stick out from the back to the front-face,
to hook into slots in the metal frame of the desktop.

So, remove the side-panels, and pinch the barb, while pushing the barb
towards the front of the front-face, to release each of (usually) 6 barbs.

* hinged at the top -- look underneath the bottom of the front-face, for something that can be squeezed, your palm facing upwards, to release a "lock", and then give it a pull towards the front, and slightly "up", in order to pivot about that top-hinge.

There are several Gateway case models. I think most of them you have to take the side panels off and the face hss some pins or straps that enter the inside of the case through the front of the computer and latch into the main case. Once you remove the sides then you can see them on all four corners. You just need to put the outward pressure on the housing face and then push the latch to the side with a screwdriver to release them.