Set up a ladder beneath the existing light fixture. The ladder must be long enough to reach reach the light fixture safely. Be sure to set it on a sturdy surface where it will not slip or wobble.
Turn off the power to the existing light fixture. Locate the breaker box for your home and shut off the appropriate breaker. This will help prevent you from shocking yourself as you change the fixture.
Unscrew the base of the existing light fixture with a screwdriver. Slowly lower the fixture from the ceiling. Set the light fixture on the ladder where possible. The ladder will hold the fixture while you unhook the wiring from the ceiling.
Unscrew the wire nuts from the top of the wires and disconnect the wiring in the light fixture from the wiring in the ceiling electrical box. Set the wire nuts aside to use later.
Remove a half-inch of wire sheathing from the ends of the wires in the new light fixture. Use wire strippers to remove the plastic sheathing.
Install the mounting bracket on the electrical box with a screwdriver. The mounting bracket and necessary screws should come with your new light fixture.
Connect the wires of the new light fixture to the wires in the electrical box. Match the black wires and twist the ends of the wires together. Screw a wire nut over the exposed ends of the two black wires. Repeat with the white wires and the ground wires.
Push the wiring up into the electrical box. Raise the light fixture to the ceiling. Screw the base of the fixture into place with a screwdriver. Turn on the power to the light fixture.