Without lights in a scene, After Effects will automatically illuminate all 3D layers equally. It makes sure the lighting stays consistent and you can focus on your project, however, adding a 3D ligh can considerable enhance the mood of a scene.

1) To see results of 3D lights, you need at least one  3D layer.

   

Enable the 3D layer switch that looks like a cube icon. You also might want to enable the lock switch to make sure you accidently move your layer.

                                            

2) Select the menu item Layer>New>Light. The light settings dialog will open:

                

•Light Type decides how the light rays are cast. Ambient illuminates everything evenly; Parallel casts straight rays as if from a distant source. More useful lights are the Spot and Point. Point is similar to a light bulb hanging in the middle of nowhere. Spot is the most versatile, as you can control how narrow a cone it casts.

•Intensity is the brightness of the light. It can be set to over 100% to blow out a scene or reduced below 0% to create total darkness in a complex scene.

        

•Cone Angle and Cone Feather are available only with the Spot light type. They control how wide an area of light is cast and how soft its edges are.

•Color is….the color of the light. The default lighting is white, but you can change it to a pale blue to cool down a scene, or a pale orange to warm it up.

          

•You can also casts shadows if you want by simply turning them on or off.

Once you are satisfied with you settings, press OK to add a light to the scene. You can edit these settings at anytime during the project by double clicking the light layer.

Press the hotkey “P” to reveal the layer's position, then Shift+T to reveal its Intensity.

As you scrub the Z Position Parameter, you will see the light move closer to and farther away from layer. The illuminated area will also shrink kas you move forward, and as you back away the layer will be illuminated more evenly.

You can also scub the X and Y Position values or put your light where you want it by dragging it around the Comp viewer. The same rules apply as for any other 3D layer: If you click on one of the axis arrows or otherwise see an exis character next to your cursor, your dragging will be constrained to that dimension.

Scrub Intensity: It controls how brightly the layer is lit.

                

Twirl open the rest of the lightsh parameters and you will notice that Spot lights are similar to normal 3D cameras in that they have both a Position and a Point of Interest. Just like a camera, the Point of Interst helps you aim the light. If the light is selected,  you will see both the lights's body and its anchor-point-like Point of Interest in the Comp panel.

    

Experiment with scrubbing its Cone Angle and Cone Feather parameters. Doing so, you can quickly achieve a variety of cool looks.