Summarize this article:

To sing classically you will need a teacher who can at a minimum offer voice coaching. Ideally, your instructor will also help you learn music theory, including how to read music.  Ask your music teacher at school about local singing instructors. You could say, “Mr. Owens, I am interested in singing classically. Do you know of a good vocal coach?” Ask friends, family members, and classmates for suggestions of good teachers. Do an internet search for instructors in your area. The best teachers for classical music have a Master's degree in opera performance. You will need to know how to read music in order to sing classically. You can do this with your instructor or on your own.  Ask your voice coach to help you learn to read music. Check out a book on reading music from your local library. Take a music class at school that teaches students to read music, like marching band. You need to learn more than just music if you want to sing classically. Find textual resources on topics ranging from the life of your favorite opera singer to vocal technique and movement.  Get a book on singing classical music from the library. A great book for this would be On The Art of Singing by Richard Miller. Check out a book on opera history. Visit the library at the local community college and check out a book on diction in classical singing techniques. Familiarize yourself with operas by listening along with the libretto, which are the written words on a page. This will help you learn to read music and understand music theory. Remember that many great classical singers are also instrumentalists! Piano is the best instrument to learn if you want to sing classically. Join the band at school or ask your parents for private lessons. Try saying, “Mom, I really want to learn to play an instrument. Can I take private piano lessons?” If you have the opportunity to learn a foreign language such as Italian, French, or German, do so. You will sometimes be singing in another language as a classical singer.  Sign up for an Italian class at the local community college. Check out an introductory textbook on the language of your  choice from the library.

Summary:
Find a classically-trained voice teacher. Learn to read music. Read about classical music and classical singing techniques. Learn to play an instrument. Learn a foreign language.