If they are rubbing just a bit each time the wheel turns, it probably means that the wheel is warped--or in other words, it needs to be trued, which involves adjusting the tightness of various spokes until it no longer wobbles when it spins. That can be tricky and should definitely be left to somebody who knows what they're doing. If it's rubbing consistently as the wheel turns, it might just be a question of loosening the nut that holds the brake on the bike, turning the brake a little so neither brake shoe is touching the wheel, then re-tightening the bolt. Many brakes also have a little adjustment screw where the cable connects to the brake caliper (the thing that rubs the wheel rim), and if you just turn it a little bit to the right, this should loosen the tension enough to keep it from rubbing. Whatever you do, make sure you test the brakes thoroughly in a safe place without traffic after adjustment, to make sure they are working well.
