Hard wiring a plug-in lighting fixture means that the plug will connect directly into an electrical box instead of being plugged into the wall. This can be useful and decorative. For example, instead of having a lamp sitting on the table, the lamp will be attached to the wall.
Ensure the lighting fixture has a built in on-off switch. Find the electrical box that the fixture will be wired to. Trace the path of the wire from where the lighting fixture will be to the electrical box. Ensure that the fixture wire is long enough to reach from the mounting place to the electrical box.
Cut off the plug of the lighting fixture. Note which wire is attached to the larger fork on the plug. That wire is the neutral wire and should be attached to the silver or white wire in the electrical box.
Turn off the electrical power to the electrical box. Cut a hole in the wall with the keyhole saw where the fixture will be, then fish the wire from fixture to the electrical box to hardwire it.
Connect the wires from the fixture to those in the electrical box. Attach the neutral wire to the white wire or silver screw, and the other wire to the black wire or brass screw. Turn the power back on and test the lighting fixture to ensure it is hard-wired correctly. Replace or close up the electrical box.
Mount the fixture to the wall.
Many lighting fixtures are designed to be hard-wired, so there won't always be a plug to cut off.
Use all proper safety procedures when working with electricity. If you don't have full knowledge of how to work with home electricity, do not attempt this project by yourself.