Ha! Yeah, thats like the easy button on the staples bissnuss depot! Sweet.
Yeah, anyhow, do the thing where you pay to ride a horse, ride the other one your allowed to, talk to indigo, get off the horse (n the riding area, not outside where you cant ride, yet, mua ha!) Play Eponas song and she will let you get on her back, once you do this, talk to indgo, twice, i think. He challenges you to race. It may be a little hard the first time, but you can do it!