Forensic pathology is a subspecialty in the field of pathology and requires you to attend medical school with a residency in pathology!
I would recommend high school courses in biology, chemistry, environmental science, and anything healthcare-related. My high school even had its own forensic science course! Getting into medical school is a huge endeavor and takes a lot of effort! I recommend trying to take some AP courses during your time in high school as well. This will set you up well for college and for being a competitive applicant for medical school!
Hope this helps
Forensic pathology, as you know, is about doing autopsies for cause of death for either homicides, suicides or other cases where cause of death is unknown. It is definitely interesting to investigate homicides and to hear what the investigators have to say and put the story together. But a lot of the autopsies are on relatively mundane things like heart attacks and stuff. Also, be prepared for decomposed bodies. This is not a field for the faint of heart or faint of smell. I was really interested in forensic pathology but I couldn't take the smell. You will be cutting open lots of bodies and the other thing you will be doing is testifying in court. Forensic pathology is a two year fellowship, but you might be like me and decide you like other parts of pathology better.
As Evan suggested you need to make sure your grades are good, you go into premed, and you get a great score on the MCAT exam so you can get into medical school. One thing you could do now is volunteer at a hospital, in any role or actually in pathology, or at a medical examiners office, to find out more about what it's like and get something on your resume. Volunteer experience always looks really good and it will help you decide if you like it.