Can you start training as a police officer at the age of 16?

Your training should have started well before you turned 16. You need to learn to read, write, and do math. All of the academics that you have been studying since grade school make you a stronger candidate. You need to develop physical stamina and learn teamwork. Sitting in your room playing Nintendo will make you soft. You need to learn honor, honesty and how to interact with others without inflaming a confrontation. Once you turn 16, you may be interested in joining a group such as the Explorers (see link).