I get this question every day via email. I figured it was time to add it to the FAQ page :)
here is a step by step with pics:
http://chevyhhr.net/forums/faq.php?faq=vb_read_and_post#faq_new_faq_item1

more:
http://chevyhhr.net/forums/faq.php

You mean to start a "New Thread" you click the "New Thread" button? That's pretty advanced stuff there.