The right hand screw rule can be used when a direction must be determined based upon a rotational direction, or vice versa. It is best illustrated using a diagram.
The axis is 'grasped' in the right hand, the fingers curl round in the direction of positive rotation and the thumb is orientated in the positive direction. Therefore if the direction of rotation is know the fingers can be curled in this orientation and the thumb will point in the positive direction, and vice versa.