You want to go from paying monthly to paying yearly? Go here, scroll down to your plan, click edit, and change the payment frequency (if you started doing it as monthly, you won't get your setup fee back, though). Did I understand what you were asking correctly?
Or were you asking something about promo codes? Those can only be used when you're first signing up, so I belive you're out of luck as far as using a promo code goes.
Very little to do with either emus or farmers!