As above, there is normally a thick threaded washer with two flat wrench sides between the calipers and the frame hole looking at the assembly from the top. You need a thin wrench to adjust it. Insert the thin wrench to grab this threaded spacer, loosen slightly, align the calipers, then tighten. If you have no thin wrench or your assembly is different, try manipulating the caliper by hand to a new dead center with the wheel off and rear bolt loosened, re-tighten then check it with the wheel on. It's minor adjustment, a few trial and errors and you should get there. If the long bolt running from brake front to back of the fork is somewhat loose, then you are wasting your time; the primary retaining bolt needs to stay tight. If any of this seems confusing, take it to your LBS, it's no more than a 30 second fix.