Hi welcome to the forums. There is a wealth of info here for both beginner and expert. I'm sure someone with more knowledge than me can help but my understanding is this.
Gordon's tutorial refers to p mode this is Program mode and is found on a canon by turning the dial on the top of the camera to P.
On a Nikon d7000 I believe it's exactly the same there are P M S an A modes.
In P mode you have full control of ISO, shutter speed and aperture to ensure you get the exposure you desire. You need to use the scroll wheel to change the exposure whilst in p mode.
The best I can suggest is experiment. Try different combinations and see what works best for you.
Whilst in the p mode press and hold the ev button and then use your scroll wheel to vary the exposure. Over or under expose. Then take the photo.
I use av mode a lot and I don't use p mode very much at all. Sorry.
With these cameras there are multiple combinations of Iso, aperture and shutter speed. All affect the exposure. Using the p mode enables you to very easily control a under or over exposed shot.
It may help to try re-watching Gordon's tutorial whist playing with your camera. I know I do !
Canon 550D, Canon EFS 17-85 IS USM, Canon EF 75-300 IS USM, Canon EFS 10-22mm USM, Canon EF35mm F2.
Got some of the gear but really still no idea...