Most universities will require an audition tape or live audition to prove you are a solid enough musician to enter the program.
Undergraduate music majors take general education classes (English, history, etc.) and also music classes like theory, music history, private lessons, and so on.
To teach music, you generally have to earn more credits as part of a teach preparation program, spend a semester student teaching under a mentor/cooperating teacher, and pass a few state tests to get certified.
After all of that, you can begin applying for jobs. :)
Some states have alternative certification programs, but those are more for folks who have built a career in some profession, who then decide to teach later in life. This path to certification is not common for music educators and still requires a bachelor's degree.
I see that you're in Michigan. Your state is known for having well respected music programs. You could gather more information by attending one of their college fairs (sometimes your school or district will hold these), by talk to your school career or guidance counselor, and definitely go to the school of Music websites for your near-by colleges and universities to read about their specific entrance and audition requirements. Many schools will be similar, but every school tends to have unique aspects of the process and very specific deadlines for application, auditions, and theory entrance exams.
Hope this helps!