You’re at the perfect age to start training – I think I was 13. As Daniel pointed out, you need to be patient & not get crazy with dieting. You’re young & still growing and nature will take its course. A good overall strength training & cardiovascular conditioning program will work fine. However, you definitely want to get the advice of a qualified Fitness Trainer to get you started – whether at a local gym or at school. Just a heads up – at your age, you need to avoid certain strength exercises. For now, lay off overhead presses and barbell squats – right now those exercises can do more harm than good. Everything else – go for it! One more thing – get a body fat % test done by a qualified trainer – that tells you a lot about what you should weigh. Good luck Jayden & keep us all posted.