What settings should I have my DSLR for very low light?

I have a Nikon D5100 with a nifty fifty… So, long story short, my friends want me to bring my camera to "document" us going to an abandon, haunted school. We drove to the start of the trail (we have to walk about a mile to get to it) in the day time, and there were no street lights and a bunch of trees would prob block the moonlight.So, I'm guessing I should get one of those lights camcorders use (my friends are also brining flashlights), the inexpensive ones since I'm only going up there once.SO, IF I GET A LIGHT FOR THIS VERY LOW LIGHT SETTING, WHAT SHOULD MY SHUTTER SPEED, APERTURE ISO AND All OF THAT GOOD STUFF BE?

No one can tell you what to set all that on. You can't just put in definite "settings" to cover any situation. The correct settings are whatever is needed to obtain correct exposure. We have no idea of how much light is going to be there. Just as a starter you could set the ISO to 1600 and open your lens wide open. See what you get with the camera in Aperture Priority mode and adjust as needed. If shutter speed gets very low, such as under 1/50 second, you are going to need a tripod.

The aperture should be set to a low f number - that is opened wide.

The shutter speed should be as slow as you can hand hold without any camera shake, so if you can, try to use walls etc to help support the camera. Of course do not use live view as this makes holding the camera steady much more difficult.

Wind the ISO up as high as necessary to get a useable shutter speed. Possibly auto ISO.

Review the results on the DSLR screen and adjust settings - shutter speed first- to get an acceptable exposure

http://aviewfinderdarkly.com.au/2012/02/01/digital-camera-exposure-settings-where-to-start/