Related URLs

Fantasy Skybox 

Fantasy Skybox:
https://assetstore.unity.com/packages/2d/textures-materials/sky/fantasy-skybox-18216

Fantasy Skybox FREE:
https://assetstore.unity.com/packages/2d/textures-materials/sky/fantasy-skybox-free-18353

YouTube

Demo: https://youtu.be/FI6HHl_GtEU

Tutorial: https://youtu.be/CZwStQ_VbN4

Get to know skybox on Unity3D website

Know what is skybox:
• https://docs.unity3d.com/Manual/class-Skybox.html

How do I Make a Skybox?
• https://docs.unity3d.com/Manual/HOWTO-UseSkybox.html