In the future, Classifieds may be edited or deleted from the "Settings" control panel (upper right-hand of each screen). After switching to the "Settings" screen, scroll down the list of left-hand sidebar options until you come across the list of options that relate to the Classifieds and then click on "My Classifieds" menu option, from here you may edit or delete ads.
You can also access the option to Edit or Delete a Classified via the same route you originally created your Ad. In the "Classifieds" section (first click on this tab), under the list of options to "Post Classified", you will find the option to "Edit an Ad". From here you may edit or delete an Ad (it is, in fact, the same screen as above).
From either of the above, you will find your list of currently running Ads on the default "Active Ads" tab. You can select whether to edit or delete an ad from the pull down box to the far right beside each Ad in the list, simply select "Edit" or "a Delete".