Discovering that you enjoy acting is the first step on a journey that can last a lifetime. The second step is where some "currents turn awry,/And loose the name of action." and that step is intense study to hone your acting skills (skills of observation and performance) and developing perseverance to be able to bear the "slings and arrows of outrageous fortune...and the whips and scorns of time".
Acting is a practical art, you learn by doing. So take every opportunity that comes your way to act. If there is a student drama club at your school, join it. If there isn't a drama club at your school. start one. Audition for every play. If you're cast, wonderful! if you are not cast, join the crew, assist the director, do anything to put yourself in the position to observe, contribute and learn. Learn by watching...active not passive watching! Go see plays! Does your community have a community theater? Join it. There are a thousand colleges and universities with excellent acting programs. See your school college office.
Take acting classes, singing classes, dance, fencing, gymnastic classes and any performance related class that comes your way (even yoga!). Your body and your mind are your instrument. Train them thoroughly. If a student is making a film, act in it or make your own film. Perform for student talent shows- sing dance, recite a monologue. All experience in front of an audience is valuable, even experiences that are disastrous.
And read, read, read! Actors are some of the most widely read people I know. The history of acting in the theater and on film is fascinating. Read actors biographies, read history and novels, write one. Read poetry. and read plays. Start from the beginning, before the Golden Age of Greek Drama, and read right through to the present day. Know what's happening out there in the field of dramatic literature.
Acting allows us to experience the world in a unique way, a way that can have a profound effect not only on our self, but on members of the audience. It's a great thing to discover you enjoy acting. Now it's time to get to work. and that where the real joy lies.