How can a teenager fulfill their sexual desires?

You should get married if you are able. If you are not able, then you should fast, for indeed it weakens desire, according to the Prophet's (peace and blessings be upon him) saying: "O young people, whoever among you can afford to marry, let him do so, for it helps him lower his gaze and guard his chastity. And whoever is not able to do so, let him fast, for it is a protection for him." Avoid the causes that stimulate desire, such as inappropriate sights, vulgar films, and music. Occupy your time with beneficial work, and recite the Quran frequently, and read the biographies of the righteous, and keep company with the righteous, and avoid those who distance you from Allah.