If you want your ad to appear higher in the search results you can pay to boost it. This will bring it to the attention of people who only look at the most recent ads on DoneDeal.
If you want to boost/renew your ad on DoneDeal just follow these instructions:
You can access your ads by going directly to DoneDeal and logging into your account and then simply just click "My Ads" in the toolbar at the top of the page.
When in your account follow the link to view your placed ads and you can manage and boost your ad from here.
Follow the step-by-step instructions to pay for your renewal.
Please note that it is free to edit any of the content in an ad. However if you want to move it back to the top of the search pages, go to Manage or Boost on the home page and this will be charged.