Sometimes an overhead light is either to dim or too harsh to bring out your true beauty, so you may choose to install a lighted wall mirror to see the real you.
However, many lighted mirrors require hard wiring rather than a simple plugin, so you'll need a power source to tap into for the mirror.
While the overhead light may not provide the type of lighting that you require, you can use it as a source of power for your new lighted mirror.
What you will need to power your lighted mirror
Drill or utility knife for opening in wall
Philips head screwdriver
Wire nuts and electrical tape
Wire cutter/stripper tool
You will need to determine the amp rating of the circuit that is powering the overhead light before choosing the proper gauge (thickness) of wire to buy. Look at the circuit breaker that controls the power flow to the light fixture. If it is stamped "15", then it is powered by a 15 amp circuit and you'll need a three wire sheath of 14 gauge wire. A 20 amp circuit will require 12 gauge wire, which is heavier to handle a higher power load.
Wire is sold in various lengths, with the smallest bundle at 25 feet. This should suffice for this task.
Preparing the intended location of the lighted mirror
When the location has been chosen, you will drill or cut a 1/2" hole in the wall near the point where the wring will be connected. Look at the back of the lighted mirror for this location.
Preparing the overhead light connection and running the wire to the mirror
Turn off the circuit breaker before you begin to remove the overhead light fixture from the ceiling. You can then loosen the two screws that secure the light to the ceiling. You'll need to support the fixture after removing the screws, because it will be hanging by the wiring.
With the light fixture suspended from the ceiling, you will begin to feed the sheath of wire into the opening in the ceiling and in the direction of the mirror location. You may need to wiggle the wire sheath until you can see the end of the sheath through the opening that you created in the wall.
Pull the end of the wire sheath through the wall opening until it extends at least 6" from the wall. You will then use the wire stripper toll to remove 3/4" of insulation from the ends of each of the three wires in the sheath.
Wiring and installing the lighted mirror
Twist the end of the black wire from the sheath together with the black wire of the mirror, then twist the two white wires and two green wires together in the same manner, Twist a wire nut onto each of the pairs of twisted wires until like the nuts are tight, then wrap the open end of the wire nuts with a few layers of electrical tape.
You can then few the mirror into the wall, using the stick level (or a smart phone level app) to ensure the the mirror is level.
Connecting the wiring to the overhead light fixture
Use the wire cutter to cut the sheath at a point that leaves ample length to connect to the wiring at the light fixture, then strip the individual wires inside the sheath as you did at the mirror location.
Remove the electrical tape and wire nuts from the wiring of the light fixture, then loosen the green screw on the fixture that secures the green ground wire to the fixture.
You can then twist the green wire to the green wire from the cheats, then twist the ends of the two black wires and the two white wires together. Twist a wire nut onto all three sets of twisted wires, then wrap the ends of the wire nuts in electrical tape.
Push the light fixture against the ceiling and secure it with the two screws, turn on the breaker, and try out your new lighted mirror (after you've freshened up from your hard work for best results).
Check with someone like Richardson Charles E Electric for more information.