Welcome to the forums
You don't want to be bowling too many prolonged spells at 100%, for obvious reasons, so don't get carried away with pace..
Im not going to harp on about how you should concentrate on accuracy, because if you have the natural gift for speed, it would be foolish not to concentrate on it..
Anyway, Im a 17 year old legspinner, but due to some pretty nasty finger injuries, I have got quite a bit of experience bowling quickly..
1) Don't bother with a run up that starts near the boundary. It is harder to keep rhythm, let alone energy when you are running miles before you bowl. I used a 12 stride run up when bowling FM, I guess someone looking for speed at our age would use about 14.
2) The run up and approach to the crease should be easy and fluid.. Just watch some tapes of Allan Donald and Michael Holding if you want to see the best approaches in the game
3) When you near the crease, attack it like nothing else. If your run up was relaxed you should have lots of energy to do this. Really get close to the stumps, and follow through fully.
4) When not on the cricket field, develop your fast twitch muscle fibres by doing short sprints, shuttle runs etc. Hitting the gym to improve your upper body strength will also do you no harm. But at 16 you don't want to be doing anything too difficult because your body is still developing
5) Most of all have fun, make all the contacts you can on the cricket field.. Network like mad with experienced pro's and coaches. They will never be short of advice to an aspiring quick.
Good luck!