You can also simply post a new ad by copying the details of the existing Ad and posting a new version. Please delete your old ad before posting your new one, if you don't delete it you will see a duplicate error that tells you, your new ad is too similar to an existing one.
Remember your ad will expire in 60 days in all categories.
So the good news is you don't have to wait till your ad is close to expiry, you can simply delete your current ad and post a new one anytime so that it's closer to the top of the category it's listed under.