Alot of practice and a voice coach just like others have said. You should also try and see what types and melodies of songs suit your voice best as it will help to learn quicker and develop your voice in a better way.
You can enroll to singing school. They will teach you how to control your breather and give you exercises on how to make you vocal cords stronger and I believe there are techniques to amplify your voice better.
just practise singing because practise makes perfect,,you dont have to be ashame of,,just prctise and practise,,until you succeed,,singing is not easy to learn you have to spend more time to practise,,,,,but if you are willing,,just do..
Have you thought about taking lessons from a voice coach? If you are in a larger city there are professional coaches that just do this job. If you are in a small community consider talking to the vocal instructor at the local school or university.