How do I become happy with myself and establish a positive self-concept?

Keys to happiness. To be happy with yourself, you must live in alignment with what matters most to you. Identify your values, then focus on building health habits to keep you on track, building positive relationships to support you, and finding a way to make a difference in the lives of others. Too many people spend too much time focused on themselves. Contributing positively to others usually works much better!
Better question. Why do you not feel happy with yourself? The best person to discuss this with is a good clinical psychologist, particularly if you can open yourself up enough to listen to what they have to say.