Hey, sounds like your BMI is in the healthy range (you can check on the NHS website) so I wouldn't stress about losing weight, especially at your age (although obviously feeling self-conscious sucks). Building muscle and developing healthy habits would definitely be great to do though, as long as the changes you make are sustainable. I would recommend trying out a few sports or different types of exercise to find what you enjoy, you could try workout videos on YouTube, e.g. dance workouts, HIIT/circuit training, pilates or yoga, or join a local sports team or gym, or try taking up running (the Nike Run Club app is really good). Joining a gym would be best for building muscle IMO, but if you do, it's important to lift weights with proper form - maybe ask a friend who lifts or employee at the gym to show you how to do the exercises properly, or watch a few YouTube videos. In terms of nutrition, to build muscle you need lots of protein (think meat, fish, tofu etc), and try to find some healthy recipes to cook, not only is cooking a great skill to have, but homemade food is often healthier and can be fun to experiment with difference recipes. Remember to be kind to yourself and make sure that any changes you make are sustainable, it's not worth hating life just to lose a few kgs. Good luck! x