To install a dome light in a vehicle, first choose a place in which to install it, and cut a 1-inch slit in that location. Feed an insulated wire under the headliner and through the slit. Install the dome light base. Connect the positive wire to the wire fed through the headliner, and place a bulb in the dome light. Apply the cover, and connect the wire to an available fuse in the interior fuse panel.
Some vehicles have stock dome light mounts. These can be found by feeling for them through the headliner. If one is not present, carefully measure the width of the vehicle's ceiling. Mark the center location; this is where the dome light should be installed.
In order to feed the wire under the headliner, the trim must be removed. First find the interior fuse box panel. Remove the trim from that side of the vehicle. Attach the insulated wire to a coat hanger that has been bent straight in order to efficiently feed it through. Once the wire is through the slit with enough length to comfortably work with, detach the hanger.
When mounting the dome light base, make sure to do so on the vehicle's structural cross beam. This prevents damage to the roof. Attach the dome light's ground wire to one of the screws used to secure the base.
When connecting the positive wire to the insulated wire, use a butt connector. To use this, put a stripped end of each wire into opposite ends, and compress the connector with pliers.