Bobby,
If you will navigate to the "Settings" screen (upper right-hand corner of your screen), you will find the option to edit your Classified Ad in the left-hand sidebar menu (scroll down a bit to find it). I believe you will get there from the "My Classifieds" option, but don't hold me to it as it has been awhile since I placed a test ad as a normal user (admins have a totally different edit path).