Choose a ceiling electrical box, in which the floodlight switch and a circuit that can handle the extra load will be installed. Switch off the connection to this circuit at the main panel, then bore a hole through the electrical box by using a small drill.
Install the cable for the floodlight. Use a cable clamp to secure the cable to the box and use wire connectors to cover the wire connections.
Set up the switch box by outlining the interior switch box on the wall, then use a utility knife to cut out a section of the wall.
Install a cable going down from the ceiling electrical box to the switch box and clamp the cables as in step 2.
Set up the weatherproof fixture box so that it solidly supports the portable floodlights. Mount the box on a level platform supported by L-shaped arms for stability.
Diagram the fixture box on the outside wall, then make a cutout, avoiding wires and pipes.
Secure the cable to the light fixture box by using a cable clamp, then follow the manufacturer's instructions to install the box on the wall.
Attach the wires to the switch box. Cover the wires from the neutral-colored incoming and outgoing cables with wire connectors and connect both wires from the black cables to the terminal screws on the switch.
Put together two bare-copper ground wires and tie the other end to the switch if a ground screw is available.
Assemble the light fixture after reading the manufacturer's instructions and connect the wires from the floodlight lamps to the incoming cable in the switch box.
Cover the perimeter of the switch box with a caulking agent.
Finish installing the bulbs.
Turn on the switch to test the floodlights.