To install a replacement automotive bulb, locate the cover or lens that protects the original bulb. Remove the screws from the frame, and pry off the cover. Grasp the bulb around the base, and pull or twist it out. Insert the new bulb, and replace the cover.
Most automotive bulbs have snap-on or screw-on covers that can be removed with a screwdriver and a pry tool. When changing headlights, you may need to open the hood to release the cover.
Once the bulb is exposed, look for a wiring harness. If the bulb has wires, disconnect them from the vehicle before touching the bulb. Put on gloves, and examine the way the bulb connects to the vehicle. Some bulbs pull straight out of a socket; for others, you must lift up a metal locking tab to release the bulb. Smaller automotive bulbs, including license plate lights, may twist out of the housing.
Keep the new bulb in its packaging until the old one is disconnected. Insert the replacement bulb into the socket or housing, lining up the connectors. Tighten it or push it in, and reconnect the wires if necessary. Turn on the vehicle to test the new bulb. Replace the cover or lens.