Why dose my landscape material black?

When I try to make a landscape material, the material is always looking black. I’m doing it as the documentation instructs, but it’s always black. Though I think that the problem maybe that the Used with Landscape checkbox isn’t in Details, under Usage, and it’s the only thing that I’ve not touched. So, I think that might be the reason that my landscape material’s black, and where’s the Used with Landscape checkbox? Is it in a different location? Or, is there another way of doing it?