Loosen the screw that holds the brake pad holder to the caliper arm. You may find the holder can then be adjusted. In most cases there is a domed washer that allows the holder's angle to be changed. Adjust so that when the front end (tip, or toe) of the pad touches the rim, there is a slight gap between the back end (tail, or heel) of the pad and the rim. That is called "toe in". Then tighten to screw to hold the pad in that position. Make sure the pad doesn't touch the sidewall of the tire. With older brakes, you used to have to bend the caliper arm to achieve toe-in. Now almost all modern brake pad holders are adjustable.