Just to double check I'm powering theboard for my project off a 9volt battery
Just a heads up, if you start experiencing any "random resets" or anything of the sorts, there's a good chance it will be your battery. 9v aren't the best choice for running anything other than the board.. if you're trying to use any motors with it, I HIGHLY suggest a different setup of batteries. 
But anyways, you'll want to use the "VIN" pin, and the ground. The VIN pin is routed to go through the 5v regulator that's on board.
Positive of battery goes to VIN.
Negative of battery (this is the GROUND of the battery) goes to, well, GROUND on the Arduino.
BEWARE:
There is no protection diode when you use VIN, so if you hook the battery up backwards, your Arduino might start smoking! (not the good kind either ;))