To enable Enlighten Realtime Global Illumination in your Scene, open the Lighting window (menu: Window > Rendering > Lighting) and enable Realtime Global Illumination.

To disable the effect of Realtime GI on a specific Light, select the Light GameObject and, in the Light component, set the Indirect Multiplier to 0. This means that the Light doesn't contribute any indirect light to the Scene.

To disable Realtime GI altogether, open the Lighting window (menu: Window > Rendering > Lighting) and uncheck Realtime Global Illumination.

For detailed step-by-step advice on using Enlighten Realtime Global Illumination, see the Unity tutorial on Precomputed Realtime GI.

Note that Light Probes behave differently when you enable Enlighten Realtime Global Illumination.

In order to react to runtime changes in Scene lighting, they sample lighting iteratively at runtime.

When you disable Enlighten Realtime Global Illumination in a Scene, Light Probes only use baked lighting data. This means that they don’t react to runtime changes in Scene lighting.

If a Light also casts shadows, Unity renders both dynamic and static GameObjects in the Scene into the Light’s shadow map. The Material Shaders of both static and dynamic GameObjects sample this shadow map so that these GameObjects cast real-time shadows onto each other. The Shadow Distance setting determines the maximum distance at which shadows begin to fade out and disappear entirely, which in turn affects performance and image quality.

Enlighten Realtime Global Illumination results also include soft shadows, unless the Scene is very small. These shadows are typically more coarse-grained than what lightmapping can achieve.

To modify Shadow Distance settings, navigate to Edit > > Quality > Shadows.