To install a new light fixture, make sure the power is turned off, and know what the different colored wires mean. Copper wire is ground wire, and it is green. White wire is neutral, and black or red wire is the current wire.
When turning off the power before installing a light fixture, just flipping the light switch in that room is not enough. The power needs to be turned off for the entire area of the home at the breaker panel or electrical panel. This prevents accidental electrocution while working with the wires.
Unscrew the plate holding the previous light fixture in place, pull it out slightly, and disconnect the wires. Pay attention to the wires and where they are connected, as you need this information to install the new light fixture.