HGG Community Forums

On your Stable Overview page you should have a box with something like this in it:

You have earned 175 stalls. Create and breed more horses to earn more stalls.
97 xp to next bonus stall

Basically how it works is that every time you create or breed a horse, you get one 'xp' point toward your next bonus stall. There are some things you can do to lose those points... I think one of them is selling them to the game auction buyer via the public auction.