No one can teach you how to become yourself, to take charge, to express yourself. Don't stand on the sidelines. Get involved in new projects, new ideas and challenging assignments. Get up to bat as often as you can, and practice your skills as much as possible. Take responsibility for your failures.
True leaders blame no one but themselves.
Leaders learn through reflective experience. Some experiences were negative, such as being demoted or fired. The key is to learn from such setbacks. Crisis has a way of revealing who we really are. Taking too much credit.