They used the buffalo for meat, fur, bones for weapons, the stomach dried out and used for a bowl, the horns also for weapons, silverware, even jewelry.
the hide was used to make clothes (leggings), tipi's, moccasins, parfleches (bags for carrying belongings), harnesses, dolls and shields. the shoulder blades and bones were used to make hoes, knives,...
Buffalos were used to make materials for the Plains Indians because that was their main animal at the time, and the easiest to find. Some techniques they used to hunt buffalo were stampeding them off...