Optimus 120-2117 - Manual (Page 6)

Follow these steps to mount the stereo.
1. Disconnect the cable from the vehicle battery's negative (-) terminal.
2. Temporarily disconnect the wire harness and antenna.
3. Lift the top of the outer trim ring then pull it straight out to
remove it.
4. Insert both of the supplied keys into the slots at the middle left and
right sides of the stereo until they lock into place, and slide the
sleeve off of the stereo.
5. Slide the sleeve into the dash and bend out all the side tabs with a
screwdriver to secure the sleeve.
6. Reconnect the wire harness and the antenna.
7. Slide the stereo into the sleeve until it locks into place, then
attach the outer trim ring to the front of the stereo.
8. Use the supplied hardware to attach one end of the supplied metal
strap to the bolt on the back of the stereo. If necessary, bend the
metal strap to fit your vehicle's mounting area. Then attach the other
end of the strap to an existing bolt on a solid metal part of the
vehicle. This strap also helps ensure proper electrical grounding of
the stereo.
9. Reconnect the cable to the vehicle's negative (-) battery terminal.
Then install the stereo's faceplate.
Removing The Stereo From the Dash
If you ever want to remove the stereo from the dash, follow these steps.
1. Disconnect the cable from the vehicle battery's negative (-) terminal.
2. Remove the metal strap attached to the back of the stereo.
3. Insert the left and right supplied release key (with tooth up) into
the slot on both sides of the unit until the locking tab is released.
Be sure R and L (printed on the keys) face out.
4. Pull up and back on the key so that the tip pushes down onto the
release catch. Then slide the unit out of the sleeve.