Shut off the power to the fluorescent circuit at the main power panel. Climb up into the ceiling space and locate the fluorescent light fixture to be removed. Unlike residential light fixtures, fluorescent fixtures are usually installed through the ceiling, which means the mounting screws are in the ceiling space above the fixture. Check to see if there is a transformer wired between the light fixture and the junction box that supplies the light with power. If so, disconnect the wires on both sides of the transformer and remove the transformer.
Remove the mounting screws holding the light fixture in place. Remove the light fixture. If the original location of the fluorescent light fixture leaves a large hole in the ceiling, that hole has to be covered to allow a residential incandescent light to be installed. Cut a piece of drywall to fit and close the large hole. Go downstairs into the actual living space to mount the incandescent fixture.
Mount the incandescent fixture to the ceiling drywall using mounting screws. Run the wires from the fixture up into the ceiling and over to the power junction box. Connect the white wire of the fixture to the white wire or wires in the junction box. This forms the first splice. Connect the black wire of the fixture to the black wire of the junction box, forming the second splice.
Secure both splices with plastic twist caps, which cover the exposed metal of the splice. Screw in a light bulb and turn the power back on. Test the circuit by turning the light on.