I'm 18 although when I started doing presentations I was about your age. I started with connecting with biology and zoology teachers at the local schools, which you can still do even if you don't attend the schools. I also do talks with the herp society I am in. That will give you a great deal of experience and hands on teaching with someone their to back you up if you get stuck. So if you can get involved with a local herp society that can also be great for getting started.

Mike