You go to home, then Terragen support, then upper right there's a button called new topic, click that and give it a title and write down your query.
If you ever start posting your work, it's the same procedure (but then in home; image sharing). Once you have your new topic, it's a thread and people can answer there, or you can post new iterations of ongoing work in that thread. For a new subject, start a new topic.
I hope this gets you on your way