Do I need to lose weight first, or begin to gain muscle?

I'm 16 years old, 5 "11. I weighed myself today and weighed 156. I usually gain and lose two pounds so my weight boggles through 154-156. I used an online weight calculator where it tells you your body fat percentage and I got 15%. The thing is I don't exactly look "fat", my parents and friends say that I don't look fat at all. All I have in my body that I really, really don't want is love handles. Other than that I have a pretty flat stomach and I want to know if I should lose the weight or just begin gaining muscle. Please answer.Do I need to lose weight first, or begin to gain muscle?
You can do both at the same time. It is a myth that you need to do one or the other first.