Electric Sunroof motor problem

I have removed the motors to sort out the sunroof as it would not tilt back in. Looks like the runners are bent. But on refitting the motor it has lost its position, as I ran it off the rail. So now it tries to open too far and does not have the tilt first stop when opening. I can see the little encoder wheel and microswitch that must be telling the ecu where it is in its rotation. But where do you make it start on the wheel/microswitch?

Many thanks.

If it is the same as the controller on a Range Rover Classic then you need to turn the wheel until you can see the "V" grooved notch in the centre of the the little cut out window.