Before attempting to Post an Ad, you should have already created an account (by clicking on the blue signup button in the top right hand corner of your screen).  This button will appear once you select an item from the "View/Post" menu from a particular Category (Items For Sale, Yard Sales, etc.).  Click here to see what your Dashboard should look like.  Then (and only then) should you proceed by selecting a menu item from the left hand column below...