To edit an existing advertisement, log in to your account move to the advertisement you wish to edit, and click on the 'Edit this advert' link underneath it.
You will now be presented with a preview of your advertisement as it now stands. To edit an aspect of your advertisement, all you need do is click on the appropriate section in the red bar on the left of the screen titled 'Edit Advertisement'.
Once you have made any changes to your advertisement, click on the 'Submit this Advertisement for Audit' button at the bottom of the preview page. This will re-submit your advertisement for audit so that it may be re-inserted in to the directory as soon as possible.