Fine tuning sidepulls becomes an acquired skill, with alot of "feel" involved. Basically, loosen the fixing bolt on the back side of the fork (front brake) or brake bridge (rear brake). I'd guess that this will take a 5mm hex wrench if the bolts are the recessed style, or a 10mm wrench if not.

once the brakes are loose (just loose enough to rotate back and forth without binding), lightly tighten the nut with one hand while holding the brakes with the other hand - the trick here is to hold the brakes with a slight overcompensation for the torque of the bolt tightening. start by holding the opposing brake pad all the way to the rim. Now start to torque the bolt a little more, observing how the brake calipers are rotating (if at all), using the free hand to prevent the calipers from rotating too close the "centered" position. The spring will have a tendency to "load up" as the bolt is tightened with the calipers restrained, so it is not uncommon for the calipers to turn farther than the angle they were being held at, hence the "over compensation". There are more sophisticated ways to do this, but this is a quick and easy way that gets you 95% there.
Looking at your photo, it is clear that the front brake is turned as a result of the tighening torque, so it is skewed (hence the brake rub). Loosen it, hold those calipers,re-tighten. Rinse and repeat until the caliper stays centered.