You Can Watch The Demo Video For Better Understanding 

General Controls :

Planet surface

-to edit the planet surface tweak the color ramp. you can add more color variation to the land surface and control how much of the planet should ocean.

Clouds

To edit cloud settings tweak the cloud mapping , and cloud colour. 

atmosphere

To edit atmosphere setting tweak the atmosphere colour,and the density.

importing :

-to import the planet to your scene you need to append the files

-after creating your planet click save and open your scene and go to file > append > PlanetGenV1.blend > collection > My Planet

-now the planet you created will be in your scene