I'm going to reply on the extreme off chance that this is an actual, legit question and not some creepy old man getting his jollies or a viral marketer looking to peddle porn.
Okay, now that that has been said, the first thing is to understand your anatomy. A decent overview is here: http://www.webmd.com/infertility-and-reproduction/guide/female-reproductive-system-overview
-- it also covers pregnancy which you might as well read about while you're at it. The main pleasure center for women is the clitoris. Locate yours (not while you're driving, of course
); you can figure it out pretty quickly because -- it should be no great surprise here -- it's going to feel good to touch and stimulate it.
Stimulate it long enough and without interruption and you should be able to orgasm. You may find you need additional stimulus such as lubrication, or something to stimulate your imagination, such as pictures, fabrics, sounds, sex toys or stories. Experiment and find whatever works for you.
As for why you haven't been able to orgasm during sex, that does happen, too. There are women who just aren't stimulated enough by penetration. In this area, experiment as well -- you may do better with oral sex only, or oral sex with simultaneous digital stimulation, or just digital stimulation. Or maybe you haven't been with a guy who's been attentive enough to your needs in this area. You could even be a woman who is not sexually stimulated by men (e. g. a lesbian or perhaps bi). There are any number of reasons why sex does not work as an orgasm factory.
Finally, there are reasons why some people just can't orgasm, no matter what. Once an organic reason is eliminated (e. g. see your doctor and ask him or her this question), you might want to explore possible psychological reasons, such as sexual or other abuse.
I do hope this works out for you as it can be rather frustrating.
And, a word to all responders on behalf of the Moderating Team
-- any spam or porn that is posted will be eliminated from this board. We take such things seriously here. Thank you.