I have found that you have to open a forum group--the General Forum is the most popular. There you can find the "New Thread" button. You can also click on the breadcrumbs (the path that you are in), found at the top of the page under the banner, to the left of where your login name shows. You can click on any portion of the path to get to where you want. I have also found that if you do post to a more specialized forum, such as Electrical, your posting title will also show under the New Posts frame to the right of the home page.
I hope this helps.