Wiring Light Fixture Video
To wire a light fixture safely, start by turning off the circuit breaker feeding that circuit. Use a tester to be sure there is no power in the wires. Trim about an half an inch of insulation off both the white and black wires. Put up the mounting bracket for the light fixture and then start wiring in the fixture. Use wire nuts to connect the black wire to the black wire and the white to the white. Connect the bare copper ground wire to the green grounding screw in the electrical box.
As a precaution, don't touch any bare copper wire except for the ground wire.
Most new light fixtures come with insulation to keep the heat from the bulb from cooking the wires. Be sure to install this insulation. Mount the fixture to the mounting bracket. Add the decorative shade and you are ready to go. Turn the power back on and your light fixture installation is complete.