Taking a protein supplement is fine, but its not required, because one can get their suggested amount of protein per day through normal food consumption. If you wish to supplement with protein to attempt to get your suggested protein requirement, this would be fine.
Its NOT protein---BY ITSELF--that builds muscle, its the "totality" of the diet, with the almighty calorie playing the most essential role in building muscle mass--as long as their is "proper" bodily stimulus being applied.
Diet is always essential, but it is especially essential if one is in their "initial" youth growth period. Since you are in this period, your diet "circumference" is especially important, IMO.
IMO, you are going to grow "some" muscle because of your age (15) as long as diet doesnt hinder your genetic growth potential during this period.
Additionally, with proper fitness training, you can "assist/enhance" this potential by providing the body--as reason to do it.
Putting this as simply as possible, if your diet circumference is good (meaning good fats, carbs, and proteins, along with proper calorie consumption), and you provide adequate and progressive fitness training, you will have a foundation for improvement in your muscle growth potential.
YOU ROCK ON, young man.
I wish you the best in what you seek to do.
Chillen