Yuhooo...Anne! Here is an example of how to start a new topic.

Let's say you want to start a new one in the WELCOME section. First you would go to the MAIN INDEX and then click on the WELCOME section. When that screen opens up, look at the top on the right-hand side. The first button should say "POST." Click on that. Put in a subject in the SUBJECT line and of course whatever you want to say in the body. Hit submit! That is how you start a new TOPIC/POST.

As far as "flat mode" goes...I THINK it means that only the beginning topic is shown when you click on that. I'm not sure about it though so don't hold me to it.
Hope that helps! JJ