I think I am as confused as others here...

[fisionchips]

I bought two items from the Unity Asset Store thinking what I was getting were terrain textures bundled.   These turned out to be substances?  How do I create the textures using them?

Thanks

[Jeremie Noguer]

You can export bitmaps out of your substances using the little cog wheel icon in the top left corner of the substance inspector.

[fisionchips]

Sorry for the delay in replying.  I have tried this in Unity and receive the following error:

Failed to generate bitmap from Substance
UnityEditor.ProceduralMaterialInspector:ExportBitmaps(MenuCommand)

[Jeremie Noguer]

Modifying a bit one of the parameters of the Substance before exporting should solve the issue.
It should be solved completely in the upcoming 4.1 though.