OK, they are single pivot side pull calipers. These are a bit tricky to center and usually require a thin 12 or 13 mm open end wrench to do it properly.
There should be wrench flats behind the brake arms and just in front of the fork or rear brake bridge. Put the wrench on these flats, loosen the mounting nut slightly, pivot the brakes to center the shoes using the wrench and hold them in position while retightening the mounting nut.