How can i make my penis longer?

You can't: There are no known cures or treatment options to enlarge or lengthen one's penis. There are vitamins that will promote this but none have ever been shown to be helpful.

You're doomed.: Maybe you'll have better luck in your next life, although a short penis isn't the worst thing to be born with. A doctor friend of mine suggests that "if you're overweight, losing weight will make your soldier stand prouder." excess fat around the base of the penis makes it appear shorter than it really is.

Enlarge your penis: There are medical and hormonal treatments, that could help maybe to make your penis thicker; also there are some surgical techniques to enlarge maybe 1 to 2 centimers your penis, each one have risks. I would recommend to see an urologist.

Yes: There is no known medicinal or herbal or surgical means of permanently enlarging your penis after puberty. There are many "snake oil" salesmen out there. Especially on the internet. Save your money.