See if there are any music schools in your neighbourhood / country where you can go and audition for to see if they'll accept you into their programme.
These schools can offer great education and help put you in touch with the right people to help further your career.
In addition, I'd suggest checking out bands that are in need of (lead) singers and audition.
Basically: Get out there and get an education in music if possible!
About your question what to do when you get there....
I've considered a career in music as well. In fact, I auditioned for two esteemed music schools in my country. I got rejected at one (only less than 1% out of all applicants made it in at the time...). I still had an audition at the other one, but decided to go to a university and check out a degree in English instead.
Why?
I realised that even with a special degree, most singers have to resort to teaching to earn their daily bread which wasn't something that I was interested in. I decided to peruse music as a hobby and now, 6 years later, I'm very happy I made that choice.
But of course that's just my story and it doesn't have to be that way for you. So, if you're motivated and excited about it, go for it! Just know that you need to be very, very prepared to work for it.