In order to promote your ads first you must navigate to your submitted ads and from the action menu select last option. It will open modal with list of all available promotions on market as well as your currently active promotions for the particular ad.

List of available promotions are:

Bump Up Ad ( this will update creation date while expire time remains and can be used only once per ad )
Highlight Ad ( this will make your ad stand out from others in listing )
Top Ad ( make your add in the first XX positions of listing as well as in it’s regualr listing position )
Urgent Ad ( display urgent ribon on ad box )