To become a veterinarian, you must maintain an excellent GPA in high school. Go to an accredited college and study and earn a Bachelors degree in pre-veterinary medicine, biology, or another science. Again, maintain an excellent GPA. Apply to Vet school to earn a 4 year degree - Doctor of Veterinary Medicine (DVM). Finally, you'll have to take the Veterinary licensing exam. If you do well on all these things, you should be ready to find a job with an established clinic and eventually open your own clinic.
I would strongly advise that you volunteer or get a job at a veterinary clinic. It can be a very stressful environment, so it would be good to explore before investing many years earning degrees to become a Vet. I once thought I wanted to be a vet, but found that I really enjoy work WITH animals rather than ON them.