Take the cable off, take the brake off the bike, clean it, make sure that the springs are working and the action is in good order, the two nuts(acorn and regular) on the front adjust the action of the brake arms, now reinstall the brake on the frame and tighten it centered, reinstall the cable(clean and grease) and tighten it, if the brakes are rubbing on one side or the other use a hammer and flat screwdriver to center the pads on the rim by tapping the spring on the side that is further from the rim, lightly, make sure the cable isn't to tight to allow the rim to spin without hitting, leaving the brake-frame-lock nut loose will only allow the brakes to self adjust continually and lower the effieciency of the brakes should you have to make a panic stop. Some manufacturers machine the piece holding the springs so you can make the adjustment(side to side) with a spanner wrench, most don't hammer and screwdriver always work.