In Action, a ray is a child of a light. Multiple lights can be parented to the same Rays object.
A Rays object is added to the schematic. In Result view, you can see the ray.
If there is only one light in the scene, the rays node is automatically connected to it. If there are several lights in the scene, select the light in the schematic that you want parented to the rays node before added the rays node. Otherwise, you can parent the rays node to the light or lights manually in the schematic.
Once a Rays object is attached to a light, you can see its result automatically. Optionally, you can also add texture components to a Rays object, such as glints and glows, similar to the workflow of the Lens Flare object (see Using a Lens Flare).