Go to the circuit panel for your home and turn of the breaker for the outside light.
Remove the old fixture from the exterior wall with the screwdriver. Pull the fixture away from the electrical box.
Take off the wire covers and separate each of the electrical wires. Loosen the ground screw and remove the ground wire. Set the old fixture aside.
Twist together the black wire from the motion sensor and the black wire in the electrical box. Cover the wires with a wire cover. Repeat this step for the white wires.
Position the motion sensor on the electrical box and secure with screws.
Screw the light bulbs for the motion sensor into the sockets, if none came with the unit. Turn on the power; test the motion sensor when it gets dark.