You can't create new ads using the app. You have to use a browser. When you use a browser, the 'Digest View' button at the top of classifieds forums shows you all the latest threads from the current forum and all of its subforums in one handy list. The 'Classic View' button switches you back to the normal view of the forums.
PSP & PS Vita Classifieds
Buy, sell and trade PSPs, PSP games and movies