Turn off the power.
You may find several pairs of wires in the ceiling box. Some of these wires may be wired to different circuits than the fixture you’re working on. Be safe: Use a circuit tester or turn off the power to the whole house to ensure that all the wires in the box are dead.
2
Remove the light bulb cover and bulbs from the fixture.
3
Unscrew the screws or nuts holding the fixture base to the ceiling box.
4
Lower the fixture base and remove the electrical tape or wire nuts from the black (hot) wire, white (neutral) wire, and, if present, green (ground) wire.
5
Attach the wires from the new fixture with wire nuts to the corresponding wires in the electrical box.
6
Raise and position the new base plate so that you can screw the new bolts through it to attach it to the mounting strap.
7
Screw in new light bulbs, install the cover, and turn on the power