Here is a simplified cubemap example: cubemap_example.zip (4.7 MB)
It’s based on some quite old example that used to have a car in it with multiple parts and materials, sadly I don’t know what copyright the model and cubemap texture had so I threw that out and simplified it a bit… Hope it helps, should be able to get a grasp of the usage with it at least. 
And source of the cubemap textures: Humus - Textures