If you wanna get started playing beach volleyball, the first thing you need to do is get a ball. You can either get a Wilson or a Spalding. Make sure it's an official ball, not a replica.
These cost anywhere from 30 to 60 dollars. Once you have a ball you can go down to the beach and start practicing. It's best if you can bring three other people to practice with you, that way you have the doubles. Two on two.
In school, you can play indoor volleyball, in middle school, and high school, and in college. Also, there's now the women's intercollegiate sport of beach volleyball in colleges.
In your area, especially if you're in a beach town, you can find local camps and clinics that teach children and adults of all ages. Your city may have a park and recs department beach volleyball class.
I started playing beach volleyball in Santa Cruz. I didn't get started until I was 14, but it's typical for girls to start as early as 10 to 12 years old.
There are also adult leagues, of course, if you wanna get into beach volleyball later. And those are the basics for getting started in beach volley ball.