Do any of the following in the Lighting Effects preview, depending on the type of light:
(Directional, Omni, and Spotlights) To move the light, drag the center circle.
(Directional lights) To change the direction of the light, drag the handle at the end of the line at an angle from the line. Command-drag to keep the light’s height constant.
(Directional lights) To change the height of the light, drag the handle at the end of the line in the direction of the line. Shift-drag to keep the angle constant and change the light’s height (line length).
(Omni lights) To increase or decrease the size of the light, drag one of the handles defining the edges of the light.
(Spotlights) To change the light angle, drag the handle at the end of the line.
(Spotlights) To stretch the ellipse or rotate the light, drag one of the handles. Shift-drag to keep the angle constant and change only the size of the ellipse. Command-drag to keep the size constant and change the angle or direction of the spotlight.