If you're 16 years old or under, your body is still growing so you should not do weights since it may stunt your growth and cause injuries, there is no reason for you to jump right into weight training without the right foundation. I know you want to have 20 inch arms and look like Arnold Schwarzenegger but first lets focus on building up some solid foundation.
Performing body weight exercises can not only prepare you for resistance training but it can also build muscle mass that you might be after. If you look at bodyweight athletes like gymnast they're big, ripped and strong.
If you're not sure what to do then there are plenty of classes that you can go to like boxing, callisthenics , gymnastics or basketball that will involve bodyweight exercises as part of conditioning.
Alternatively you can look up videos on Youtube Or Dtubw ( lots of bodyweight workouts can be found on my blog) that show you plenty of exercises that you can start doing today. After all, is it a good idea to start early ? Sure thing, you will thank yourself in the future for starting early. Don't be afraid to start and make mistakes, we all had to start somewhere. Before you know it you will be flexing in every mirror that you see :)