You'll need a four year college degree. Many people who wan to go into the medical field choose biology or pre-med, but really, English works too. It matters that you have the degree, and good grades and extracurriculars.
Then, you will apply to medical school. A counselor at your college can guide you through that process very easily.
After medical school (usually 2 to 4 years) you'll do your internship/residency usually at a hospital, and you can choose to do yours in cardiology and surgery. (There's more to this obviously, but this is the bare bones)
There are a few registry tests you'll take, like FACS, and then you will be a qualified cardiac surgeon