Optimus 120-2113 - Manual (Page 9)

If the stereo does not work, immediately disconnect the cable from your
vehicle battery's negative (-) terminal. Then recheck your connections.
After you verify that the display lights, follow the instructions in
"Mounting the stereo" below.
Mounting The Stereo
Once you verify that the stereo is connected properly, follow these steps
to mount the stereo.
1. Disconnect the cable from the vehicle battery's negative (-) terminal.
2. Disconnect the wire harness and the antenna.
3. Press REL on the right side of the control panel to remove it (see
"Removing the Control Panel" in Faxback Doc. # 62493).
4. Insert both of the supplied keys into the slots at the bottom left and
right sides of the stereo.
Press the keys downward, and slide the sleeve off of the stereo.
5. Remove the keys from the slots.
6. Put the sleeve into the dash, then secure it by bending out all the
tabs with a screwdriver.
7. If your vehicle has an existing mounting hole in the dash, use pliers
or a 5/16-inch box-end wrench to attach the supplied washer and the
short end of the supplied mounting bolt to the back of the stereo.
Note: The other end of the mounting bolt is covered by a rubber
mounting grommet.
8. Reconnect the wire harness and the antenna.
9. Slide the stereo into the sleeve until it locks into place.
If you are securing the stereo in an existing mounting hole in the
dash, push the mounting bolt (covered by the mounting grommet) through
the existing mounting hole and make sure it is secure.
Note: If the mounting bolt is too short to reach the mounting hole,
remove the rubber mounting grommet and screw the supplied
mounting bolt extender onto the mounting bolt. Then push the