Use the "edit" mode for an individual listing; the option to feature that listing for $2.50 then appears as a check-box. Warning: if you use a "featured" listing as a template for your next listing "list similar," be sure to UNcheck that box or else that and all subsequent listings will carry the $2.50 featuring charge forward. It can get expensive to do so. Don't ask how I know....
Comments
Just upgrade your store level to featured.