At your age I would start out using bodyweight exercises. Pushups, situps, pullups, dips, etc. Get good and strong on these before you move onto lifting weights.

you are about to start bodybuilding don’t think about creating or protein already. How to start its depends on your current body stats. if you are slim go to gym train for 15 day and then try to lift as much havy as possible with 12 to 15 reps

Lift weights using different techniques and lifts to work the different muscles such as bench press, towel bench, box squat, power clean, push press and many more. Start a diet. create a schedual doing different lifts so you dont over work your muscles. But if you dont have access to weights do push ups,sit ups, runnig, jumping and or jump rope pull ups, squat thrusts, and more. its not as effective without the weights but it will help you get stronger and faster. while doing all this drink water because not just your muscles need oxygen and water your whole body does. just be sure not to drink to much but make sure you drink enough to stay hydrated and healthy. just realize this isnt going to happen overnight it sometimes takes years to get into that kind of shape. but once you get into that shape its easier to regain that muscle if you stop because muscle seems to remember and is way easier to build back.