The active render plugin you use will determine where to adjust the skylight but I’ll bet if you’re new to Rhino you’re using the default Rhino Renderer. The skylight in that case is adjustable in the Environments panel (use the Panels drop down menu). You can make a new environment with the plus symbol and then adjust the color for the intensity. If you use an HDR texture in the environment, this image will have a multiplier value you can adjust. Think of the skylight as a light from all directions that can be based on a HDRI. The Sun is adjusted in terms of the horizon via the Sun panel.
You mention adjusting the SKYLIGHT intensity in the ENVIRONMENTS Tab. LOTS of OTHER stuff in your answer like Renderers and SUN, and even a short video showing off your ability.
Suitably impressed,
but the initial QUESTION was HOW to ADJUST the Skylight setting.
SO-
How do we adjust the skylight intensity in RH-5 ?