Haha we're a lot alike, I'm a 15-year-old sophomore too! I was on Enchantment a few years ago, but I was still in the kids club then. Here are a few tips coming from a girl's perspective:
DON'T be cocky- you'll just attract girls who are also full of themselves
As posted from the others, definitely go to the teen club the first night for the "Meet and Greet" type event (when you first go on the ship, pick up the "Teen Cruise Compass" at the main desk area so you know what time)
If you feel too umconfortable going up to girls by yourself, maybe make a few guy friends at first, and you can find a group of girls so it takes the "one-on-one" pressure off
Smile, be outgoing and friendly
As posted before from the others, asking people "where are you from" or "is this your first cruise" are awesome ways of starting conversation!
You'll have a blast, you'll definitely make friends and meet girls, just be friendly and open (NOT shy)!
I have cruise compasses from my recent cruise on Royal Caribbean and I can give you tons of more info/advice if you want, feel free to personal message me, and I hope I can help with anything else