Skyboxes missing from standard assets in unity 5

Could anyone show me how to add skyboxes in unity 5?

If you have problems with the docs:

please open a new question and explain in detail what your problem is.

To implement a Skybox create a skybox
material. Then add it to the scene by
using the Window->Lighting menu item
and specifying your skybox material as
the Skybox on the Scene tab.

original: Unity - Manual: Skybox component reference

Maybe check here for at least some infos but no explanations still: