view finder & light meter question for newbie

Hello all, I own a rebel xti and although I've taken an introductory course, i'm still feeling lost! I just purchased a book called "Understanding Exposure" and this following sentence has me stumped: "In Manual mode, adjust your shutter speed until the camera's light meter indicates a 'correct' exposure in your viewfinder and take the photograph.

what should I be looking at?

You should see something like this in the VF:

http://a.img-dpreview.com …new/canon_450d_​vfdisp.jpg

See where it says exposure level indicator. That thing should be in the center. All this is in your camera manual so I suggest reading that.