Practice singing every day frequently.

Breathing exercises, lemon honey and ginger tea for throat.

Take singing lessons from a professional.

I agree with @YARNLADY about taking lessons from a professional. One of my acquaintance’s daughters (this was about 12 years ago) wanted to be an opera singer from a very young age. When I knew them, the young lady was about 10 years old and had been singing at school from the very beginning, but because she was serious about becoming an opera singer, her mom (who was a musician and continued to take violin lessons into adulthood) hired a vocal coach for her. I was amazed at the talent this young lady had, she sounded like an adult singer. She was very dedicated, but like ballet dancers, you simply have to be coached for your entire career. It’s very rare that singers get really good simply on their own. Even most of what you hear on the radio and TV is fixed with sound editing equipment, but having a vocal coach will keep you in tip top shape and give you the tools that you need to improve and not injure your vocal chords. Good luck, and might we get to hear a sample of your singing?

Stand as tall as you can so you can take in as much air as you need to sing. Learn to sing on top of your breath. Open your mouth and let ‘er go. Sing as high as you can and as low as you can. And sing every day. Then find a teacher. Choose someone whose voice you like.

I’m not s singer, but from the considerable amount I’ve read about Frank Sinatra, he developed his unique vocal style and technique early on, in part by understanding the importance of singing lyrics with genuine, not manufactured, emotion; and learning how to master breath control.

For the latter, Sinatra supposedly jogged and swam religiously, among other things; and from watching band leader Tommy Dorsey play the trombone. Dorsey’s style was very fluid—he “slid” from line to line without appearing to inhale. Over time Sinatra developed the same kind of “breathless” technique.

Turn up the instrumental

Always keep in mind that singing is 50% hearing,i.e. train your listening to music skills. Recognize intervals (difference between pitches), recognize harmonies, recognize instruments etc.

While singing, sometimes put a finger on the entry of your external auditory canal. Check your pitch.