How?
You gotta find out what makes you lack confidence? It has to be something...lack of appreciation u get frm people, the way u speak, personality, lacking in something, etc. Once you find out what stops you from being the confident person you aspire to be, you can work on those things-correct them and you will eaisly transit from being non-confident to confident.
And i assume when you r confident, you have self esteem. I believe they r correlated.