Thanks Oshyan, I did find that documentation.
Creating your first scene is fine as far as it goes, the other stuff I'm sure explains the functions but, for me anyway, is in a very dry, hard to absorb way. A bit like reading a technical treatise. I'm beginning to get the hang of how things are structured in Terragen but it would be nice ( in an ideal world ) to have some tutorials explaining how if you create this layer, then choose this or that shader you will get this or that effect. So if I want to create sand dunes for example, there is an explanation of which shader applied in this or that way will create that effect, followed by an explanation in context of what all the myriad of other settings do, seed, lead in scale, small scale etc.
Video tutorials would be best but even a pdf with settings on one side and an image on the other showing the result would be helpful.
However, it's clear that Terragen 2 gives an awful lot for free or for a very low price and that the kind of resource I'm suggesting takes time and money to develop so maybe I'm looking a gift horse in the mouth and should stop whining and just get on with it