I have a floodlight & the socket has a blk & white wire only; I need to run a wire from a switch to the blk & white wires to turn the fioodlight on & off,but do not know how. I had it hooked directly to the breaker before, but I figure there must be another way to turn that light on & off.I got power to the light,blk to blk ,white to white,but how do I connect a switch into the blk & white wires?

The whites in the flood, stay as they are.

The blacks get broken and placed into a switch loop.

You can:
1. connect the black and white to the switch and re-label the white with black tape at the ends.
Now connect the taped white to the black power lead and the black to he black of the light.

2. (preferred) use x/3 wire (14/3 or 12/2) depending on what you have. This will have a red/black and white. Use red and black to the switch and break the black wire at the fixture and insert the red/black.

Wirenut the ends of the white wires. Later this can be used for powered timers and other automation devices.

Good morning John,

What you are looking to do is to create a "Switch Loop". This a very common wiring solution.

Install the outlet - run the cable (14/2 AWG for a 15 amp circuit) or (12/2 AWG for 20 amp).

Open (shut off the breaker to this circuit). Remove the light fixture.

You should see a cable with a Black (Hot) and White (Neutral)conductors in it along with a bare ground conductor.

Before you disconnect the light fixtures wires. Do the following: Take the White conductor that will go to the switch and either color the insulation or use a sharpie. You can use any color other than gray, white or green. The common colors are Black, Red or Blue. Do the same at the wall switch.

Next, at the switch, connect the retasked (colored) conductor to the bottom terminal for the switch. Connect the Black conductor to the top terminal of the switch.

Back at the fixture, use the retasked (colored) conductor and connect it to the Black cable in the ceiling. Connect the Black conductor coming from the switch to the Black conductor on the light. Connect the white from the fixture to the white coming from the ceiling cable.

Now here is why you did what I asked you to do.

According to the NEC, you can use the Gray or White conductor to carry power away from the supply to the switch. You cannot us it as part of the return circuit.

Switches do not use Neutral, they are Hot only, so you need to re-task the normal Neutral conductor by changing the color of the conductor.