To Add Environment Light Sources in the Rendered Output in Effects Manager

Open the Effects Manager dialog ( Visualization > Home > Rendering ).
Click the Load Image Set icon and open the desired light images.
Select Environment Visible from the light images list and turn on the On check box and then set the Intensity.
Select Environment Indirect from the light images list and turn on the On check box and then set the Intensity.

Rendered scene with Environment Visible and Environment Indirect

Note: Effects Manager will automatically create an image for Environment Visible and Environment Indirect when you choose an environment, allowing you to regulate their contribution.