Set the sail, concave side to the wind, so that its plane lies about halfway between the wind line and the keel plane. The large component is transmitted through the mast to the boat. This force can be divided into components, one along the keel forward, one normal to the keel downwind. The first is small but moves the boat quite well because the resistance along the keel in the water is small. The center of force on the sail has control of the moment applied to the boat and making it turn about a vertical axis.
Appropriate adjustment is made by moving the sail backward or forward on the mast.
Less desirably, the adjustment can be made by changing the location of the mast on the boat.