Woa there, I was just making a suggestion to explore psychology courses as an elective when you get to college if you want to get a flavor for the field. I'm well aware of the recs for medical school and psychiatry. I just finished med school and have just matched to psychiatry residency to start this summer. I'm not sure how familiar you are with the process of medical school and residency so I'll start from the beginning.
Similar to oldpsych doc's post but I'll elaborate.
1. Pre med reqs: As I said in my post, your first step is to do your pre med requirements, preferably at a 4 year university as part of your pursuit of a BA or BS. Those requirements will vary at different medical schools but they generally share a lot of the same coursework. See UCLA medical school's website for requirements, I've pasted the link below. These are college level courses, for the most part you can't use high school classes to cover these (though some schools may accept AP courses if I remember correctly but those are in the minority), Most applicants take 4 years to finish these courses and get an undergraduate degree.
Prerequisites - David Geffen School of Medicine - Los Angeles, CA
2. Extracurriculars: During that time, applicants will generally try to find extracurricular activities like hospital/free clinic volunteering/research. As mentioned in my post since you are interested in psychiatry you could pick extracurriculars that are in the fields of psychiatry/psychology like volunteering at a community mental health center.
3. MCAT: Most applicants take a summer course and 2 months of dedicated study to pass this.
4. Apply to Medical schools/obtain interviews/get an acceptance
5. Complete medical School (4 year commitment) to get a doctorate in medicine. While in medical school pursue psychiatry electives and extracurriculars.
6. Apply to psychiatry residency/obtain interviews/get an acceptance. Psychiatry residency is another 4 year commitment.
There are lots of sites with info for people just starting their pursuit of medicine. Here is one article that may be useful.
Pre Med 101 – Know What You Need to Get Into Medical School | The Medical School Headquarters
Pre allopathic forum here on SDN is a good start.
From where you are standing, finishing a psychiatry residency is 12 years away. That is if you go straight through. Therefore, its important for you to constantly be checking the field and making sure its what you really want to do. Talk to psychiatrists, learn about mental health. Its worth it if you really want it but its going to take time.