These setup instructions are for the Built-in pipeline
After importing the asset you can add Radiant GI to your scene by following these steps:
1) Go to the top menu: GameObject -> Create Other -> Radiant GI -> Radiant Volume
2) pick the Radiant Volume object you created in step 1 and either create a new profile or load one from the assets folder using the buttons available
3) Finally find your camera and add the ‘Radiant Global Illumination’ script.
You are now ready to adjust the parameters of Radiant GI by picking the Radiant Volume object you created in step 1
Tip: You can use Local volumes by picking ‘Local’ in the top-most option called Mode and adjusting the scale of the GameObject, in the scene view you will see a wire-frame box that depicts the volume covered by the effect.