The sensor has 3 wires, black, white, and red. It may have a ground, but this is not important.

In a wall switch plate, take the plate off and the switch out. Wire the white to the existing batch of white wires. Connect the black to the black that is hot all of the time, and connect the red to the black that goes to the lighting circuit.

The sensor will see motion and pass power through the red wire out to the fixtures you want to have on.