Walkthrough for This is Armadillo USA of Red Dead Redemption.
1. Meet Bonnie at her house marked with B in the map.
2. Get on the wagon.
3. Keep going toward the Yellow Mark but be careful to not hit anyone on the road, they will attack you and if you shoot them, the mission will fail.
4. Go to the Doctor's Office to meet the doctor that saved your life.
5. Buy the free Medicine and then head back to Bonnie in front of the General Store.