Renewal option

In the plugin settings > Moderation, there is a option to check Delete expire ads. There you have mentioned “If you have the renewal option enabled, this will be the number of days after the “Renewal Reminder” email was sent.”

How Can I enable renewal option, because the user has no idea what to do after the listing is expired. There must be a way to renew their ad after expiration. If they have not renewed the listing for a specific no. of days, then the ad must automatically deleted permanently.

please help me…