ACK! What have I forgotten to do?

[Zander]

Thank you, Kierra. I've tried starting again, but I'm now having problems making the terrain in the first place. I could just download the sample file, but I want to know why this isn't working.

I've asked Kato to let me have a journal so I can put all these whinges and gripes in one place.

[Chacal]

I've duplicated the bit I want to put the grass on, but I can't seem to select it outside edit mode without the original terrain being selected as well.

One way to do this is to use the "outliner". Look for it in the help.
When you have it selected, move it to a different layer. Look up layers in the help too, those are extremely important.