How to adjust the exposure settings to 0 on my nikon d3000?

I just got my nikon and when i take pictures its really dark to people recommended to turn the exposure down to 0 with the button. I try to do that but when i click or hold the button (the +/- button) nothing happens and it doesn't move to 0, it stays all the way up.

That makes no sense. You might want to try an EV of O, such as f/5.6 3200 1". Or maybe they mean set the light meter to a correct exposure in P mode, meaning don't put it to +1 or -0.3 comp. 0, no other numbers on the line thingy on the back of your camera.

Right now, just put it in auto mode and get used to having it in your hands. Read the manual on how to use it and get some books from your local library. Photography for dummies is a good book that every library in the world should have. The only thing I suggest you buy is a tripod, get a $15 folding tripod from walmart. Because when it's dark you will need to hold the camera still, ie on a tripod.

Hold down the exposure compensation button (that's what it's correctly known as), and rotate the control dial on the back of the camera.

The exposure compensation doesn't work on Auto mode. It works on the Program, Aperture, Shutter, and manual modes.