ok when you're in a section of the forum (i.e. Sexuality, Recreational, Feedback, etc etc) you know how you see all the different "topics" people have put? like it's on the left side of the page, has a title you can click on to read that thread.

ok now that you're looking in that general area, follow that left column all the way to the top and you should see a button that says "New Thread"
http://boards.cannabis.com/images/buttons/newthread.gif (thats what the button looks like)