There is no way to naturally enlarge your penis size. Jelquing actually damages the penis and the penis cannot be exercised beacuse it's not a muscle. Your penis has to grow on it's own.
You can read more about penis size in the announcement in this forum entitled "Puberty FAQ and Information - THIS MIGHT ANSWER YOUR QUESTION!"
And tell me why you need to enlarge your penis while you're in puberty. You're gonna grow anyway...wait it out!