How should I connect a fixture to this outlet?
Warning: You'll be working with live electrical wires during this procedure. If you don't feel comfortable doing so, please contact a local licensed Electrician.



Set up your multimeter (or voltmeter) to measure volts AC.
Very carefully remove the caps from the white wires, making sure the wires do not come into contact with anything.  
Turn the switch to the ON position.
Touch one probe from the meter to the bare grounding conductors.
Touch the other probe to the exposed end of one of the "white" wires.
Touch the probe to the other "white" wire.


You should have measured 0 volts to one "white" wire, and line voltage (~120 volts) to the other.  Using a bit of black tape, or a black marker. Mark the "white" wire that measured line voltage to ground.


Turn the breaker off, and verify power to the circuit is off.
Connect the white fixture wire to the unmarked "white" wire from the ceiling.
Connect the black fixture wire to the marked "white" wire from the ceiling.



  Warning: You'll be working with live electrical wires during this procedure. If you don't feel comfortable doing so, please contact a local licensed Electrician.