There are many healthy benefits of being physically active. Some of those benefits include losing weight, improving fitness and strengthening your bones and heart muscle. Physical activity is both formal, like playing on a sport team, and informal, like walking your dog.
The best way to become physically active is to decide what activities you enjoy doing. Some examples of outdoor activities are hiking, biking, skating, canoeing, and skiing. If you enjoy staying indoors and playing video games try video games such with lots of excercise and dancing movements.
Perhaps sports are what interest you, well that's great. Many schools have leagues that you can sign up for. Even if you just play sports with your friends after school, that is still being physically active. If you do not have any specific activities planned, you can still become more physically active. You can take the stairs instead of using the elevator, help out with household chores like sweeping and mopping, or you could help out with yard work.
There are many different ways you can become physically active, you should try a number of different ways until you find something you enjoy doing.