Take lessons from a professional voice teacher. You need constant feedback from a professional who can evaluate what you are doing and show you how to gradually improve it. Learning to sing is not something you can do by reading descriptions on web sites or in printed books.
The answer to your questions is the same, and that is breathing and breath support. As said by Wheat, you need constant feedback by a professional singer who can correct you and help you get the feeling, because that's what it is.