Workout naturally for as long as possible-building a good solid base and foundation is important to your growth and maintaining gains after a cycle.
Don’t start too young-it’s easy to want to jump on gear (steroids) when you’re in high school but don’t do it. Workout naturally and let your body develop as it should. Unless you’re competing wait until mid 20’s or so to start juicing, and have years of natural training already under your belt.