The Mitsubishi Lancer offers a simple design to facilitate changing your headlights. In some vehicles you have to remove the headlight assembly and other parts to access the headlight itself, but in the Lancer you do not need to mess with any other car parts except those on the assembly. The assembly is a composite system, meaning if the low or high beam lights fail you can replace it without having to replace the entire assembly.
Turn off your Lancer and prop open the bonnet.
Disconnect the wiring harness from the back cover of the headlight.
Twist the back cover off the headlight and set it aside.
Twist the socket counterclockwise to remove it from the headlight assembly. Pull the light bulb out of the socket and insert the replacement bulb.
Twist the socket to the right into its securing bracket. Replace the cover and twist it, too, to the right. Reattach the wiring harness.