Which high school courses you take doesn't matter that much, but your grade point average and test scores affect what university you can attend. From there, you would finish a 4-year university degree and then pursue a Masters degree at graduate school. As far as courses to take, you can major in Psychology and take psychology courses for your undergraduate degree, but no matter what you graduate with, you will have to apply again to your master's program and a psychology-related degree is not always a hard requirement. During undergrad, you can also volunteer or work in the mental health field (behavioral therapy, suicide hotlines, etc.) which will help your candidacy for graduate school.
During your master's program, you will participate in a practicum where you will practice under the supervision of a credentialled professional. After you graduate, you need a certain amount of hours practiced before you become fully licensed. I hope that helps!
For undergrad, you can look at this ranking of schools with top psychology programs: https://www.socialpsychology.org/gunder.htm