Installing a new light fitting or fixture in place of an old one is one of the easiest and quickest ways to transform the look of a room. Light fittings come in a vast array of styles. The process of installing them, however, is essentially the same for all styles, entailing the connection of two power wires and a ground wire. If there's not currently a light in the ceiling, have an electrician install a circuit and an electrical box there before you start.
Cut the power to the existing ceiling fixture. Take out the screws holding the fixture to the ceiling. Pull the fixture down and disconnect the wires by unscrewing the wire caps that hold them together. You will be left with a black, a white and a copper wire hanging from the box.
Unscrew and remove the mounting bracket that is attached to the electrical box.
Locate the mounting bracket that is included with your new ceiling light. It will be a metal strip or plate, with screw holes and access holes in it. Mount it to the electrical box in the ceiling using the provided screws. Pull the wires down around it so they're still hanging off the box.
Wrap the bare copper wire from the electrical box onto the green screw that's on the mounting bracket. This is the ground wire. Turn the screw clockwise to tighten it.
Position the new fixture near the box. Connect the white wire from the fixture to the white wire from the box, twisting a wire cap over both of them. Do the same for the black wires from the light and the box.
Lift the light to the box, pushing the wire connections into the box as you do so. Line up the screw holes of the light with those of the mounting bracket. Insert the screws and tighten to mount the light. Turn on the power and test the light.