The medical physics educational path, in general is:
1. Undergraduate degree in physics or equivalent.
The "or equivalent" is defined by the graduate program, but generally means programs like engineering physics, physical chemistry, BME, or dual majors that include physics. The program will need to have included courses like mathematical methods, senior level E&M, electronics, some basic programming and/or numerical methods, and a senior lab course. In some programs you are expected to write the same comprehensive exam the other physics students write so you will need to have covered enough material that you have a reasonable chance as passing that.
2. Graduate degree in physics including your CAMPEP diadactic coursework. The specifics here diverge somewhat. The most popular way of doing this is to get into a CAMPEP-accrediated MSc or PhD program. But there are also DMP (doctor of medical physics) programs and post-PhD programs that allow you to complete the necessary coursework if you did your PhD in another sub-field.
3. Clinical training (residency). Residency programs are ~2-3 year programs that allow you to complete the practical/clinical aspects of the training necessary to write your board exams. Sometimes they also double as post-doctoral research positions. Note that you are working and being paid at this point in your career.
4. Board exams. The ABR and CCPM both have staged examination processes including written and oral exams.