You first want to navigate to the "forums" page, by clicking "Forums" in either the toolbar at the top of the page just under the Open Roads Radio banner graphic or in the "Main Menu" box on the left of the page.
Note that the "home page" (with the GMT clock) is NOT the forum page.
On the forums page you will see the main forum headings, with the individual forums under each one, with little blue box icons to the left of each one.
Decide which forum would be best for the topic of your thread. Click on the forum name and all the threads in that forum will appear.
To start a new thread, click on the "New Thread" button and the editor window will open.
This forum runs on VB Portal/V Bulletin Software, which is about the best forum software out there and many hundreds of sites use it. Once you learn to 'drive' OpenRoadsRadio.net you will already know how to function on hundreds of other forums.