Not sure how best to word this without getting tedious. But this old house is such a pain. Basically I am trying to figure out how to rewire a light switch in a bathroom that used to control two separate bulbs on a bathroom ceiling. These lights were part of a recessed fixture that was part of an exhaust. The exhaust was on its own power supply and the two switches controlled two bulbs.
I hope the pics I took come through and that you can see them. The black wire from the Romex in the upper left hand corner is the only one that is hot (I used a voltage tester to confirm this). The Romex on the upper right and lower right don't activate my tester.
Not sure what other details I can provide. When the wires are all disconnected but the power to the circuit is "on" the black Romex at the ceiling is also hot.
Can anyone tell me how to rewire this so that I can get the light on the ceiling working? What was previously in the ceiling were these two recessed light bulbs that were controlled individually by two light switches which I removed and is what you see on the wall now. And now all I want to do is use one light switch to turn on one light fixture that I centered in the ceiling (pic provided).
Not sure if this is necessary but there is another light switch above the exposed plate in the photo I've provided. That one I can get to work but it will be designated for the new exhaust I will be installing that won't have a light fixture. 
Last bit of possible useful info. The gauge of the Romex located in the bottom right hand corner of the switch box is noticeably smaller so I wonder if that was to control the second light which I am no longer using.
Hope to get some input, thanks.
Best Answer
You determine which of the two cables on the right is connected to the light.
Turn off the breaker to the line hot (cable on the left). Fasten the line hot to one pole of a simple switch, and fasten the black from the candidate cable (say the upper one on the right) to the other pole of the switch. (Keep the whites out of the way for the time being.)
Turn the breaker back on and use your non-contact voltage tester to see if the black at the lamp is powered when the switch is on and unpowered when the switch is off. If it is, then go turn the breaker off and connect the white in the line cable to the white in the cable whose black is connected to the switch. Now turn the breaker on and the switch on and the light should come on.
To complete the job go turn the breaker off, fold the wires, and screw in the switch. Cap the wires to the other cable which is not going to be used. Put on a cover plate. Turn the breaker on and verify operation.
NB: You should really verify that the cable you have energized goes only to the light and not also to some other cable that should not be powered.