There are several control methods available to solar sails that can work. They were studied quite extensively by NASA during the 60s. The thrust generated by a

There are several control methods available to solar sails that can work. They were studied quite extensively by NASA during the 60s. The thrust generated by a solar sail is proportional to the angle between it and the sun, as is the direction of that thrust. If any part of your sail can twist, then you have steering vanes that are quite useful. You can twist the vanes to angles where the vane on one side of the craft is reflecting sunlight while the one on the other side is not in order to get a rotational acceleration. If your sail is carrying a payload, then that payload will likely be in the center of the craft, with the sail spread out around it symmetrically. If you can shift the payload side to side relative to the sail, then that will shift the center of mass of the whole craft. With more of the sail to one side of the center of mass you will again get a rotation. If you want more information, find a copy of the book Space Sailing by Jerome Wright; it's quite good.