There are 2 ways to renew your ad.
1. You can make a new add the same way you made your old one. (If you do this, please take down your old ad if it has not already expired.)
2. You can simply pay for the "ad upgrade" of "bump up" when editing your ad. Doing this will put your ad back to the top of a search as if it is new. Then it will be another 90 days before expire. The "bump up" upgrade only costs $1.00.
If your ad is already expired, you can still find it for 14 days by going to "My Account" > "My Posts" > "Expired Ads".