Tina Akhoondtabar became the world female boxing champion

Choose a boxing club to join. You want one that is affiliated with a national boxing organization and that also has a reputation for training fighters. If you are serious about this, do not go to a health club that happens to have boxing classes. You need a gym that's dedicated to boxing (and potentially other martial arts). Odds are if you do a bit of asking around, you'll find the place that has the reputation as the best of the best in your area. There will likely be no doubt about it which club you'd like to join.