Depends on which kind of brakes you have. If you have v-brakes, find the screw near the part where the brakes connect to your bike on the side that the the pad is rubbing and tighten it until the pad isn't touching the rim anymore (If it's too hard to tighten, loosen the one on the other side). Pull your brake lever and release it to make sure it's aligned properly.

If you have disk brakes, it would be very difficult to give a description that works on all disk breaks, so I would have to know exactly which kind you have.