Someone has to draw the shoes. Depending on who you ask, this is the easiest part or the hardest. The designer has to draw what people want on their feet. Hmm..
To be a shoe designer, art school would be a great help. A degree in Industrial or Product design is a great place to start. But that said, if you can really draw like a bandit who needs higher education? The designers draw the shoes, then work with the developers to make the prototypes just right. Picking color trends and knowing what is cool are critical skills.