In order to become a professional wrestler for the WWE or almost any other wrestling faction you need to first got to pro wrestling school. The minimum age to go to pro wrestling school is normally 18 years of age but some schools may allow you to start at the age of 17.
You can start by getting in shape and staying healthy. You will need wrestling training and experience. Contact a local wrestling club or find a company that travels around the country offering training seminars you can attend.