This outlines the differences in sailboat behavior from the standard Rover modes.
Sail position is directly controlled by throttle position. Minimum throttle is sail fully in, maximum throttle is sail fully released. You may find the controller disarms when tacking to the left travelling upwind with the sails tight. If this is an issue disable stick disarming.
The Sail is automatically trimmed to the wind direction using the wind vane. A tack can be triggered from an aux switch; the vehicle will match its current angle to the true wind on the new tack. Note that the vehicle will only try to sail if the operator is requesting some forward speed with the throttle input. With 0 throttle input the vehicle will let out its sail in a attempt to stop.
The vehicle will tack upwind back to the home location if required.