Answer:
In most cases (in the US), you cannot get into medical school from high school. you must complete your undergraduate studies (which is college) after high school. Your major does not matter on your application however, you do need to complete the courses that is required. Try to maintain a strong GPA. You also must take the MCAT, an admission test for medical school. Admission is strongly based on your GPA and your MCAT score. Try doing some extracurricular activities. this will make you become more competitive and it can make you separate out of the pack.
There are a few combined 7-year BS-MD programs, but they are generally very competitive (you can search "combined bachelors medical program" for more information).