Any way you do it, however you define it.
In other words, what “sex” even IS varies pretty widely from person-to-person and day-to-day, and can be or include ANY number of sexual (sexual: About or relating in some way to sex or sexuality.) activities. Intercourse is sex (sex: Different things people choose to do to actively express or enact sexuality and sexual feelings; often this involves genitals, but not always. ) , but so is oral sex (oral sex: Use of the mouth, lips or tongue for sexual stimulation. Cunnilingus (“going down on”), fellatio (“blowjobs”) and analingus (“rimming”) are some common kinds of oral sex.) , anal sex (anal sex: Sexual activity involving the anus. Anal sex may include stimulation with fingers, the mouth, a penis, sex toys, or other objects or body parts.) , manual sex (manual sex: Sometimes also called digital sex. Kinds of sex involving the hands and fingers to sexually stimulate the genitals or other parts of the body. Fingering, handjobs or “fisting” (deep manual sex) are some kinds of manual sex.) , making out (making out: A vague term, but often a session of extended activity that includes passionate or deep kissing, some kind of other body contact and may even include other kinds of sex, like manual sex (fingering or handjobs).) , frottage (frottage: Rubbing against the body of another person to express sexual feelings or seek out sexual pleasure. “Dry frottage” is done with clothing on (“Dry humping” is a form of frottage).) , role play, cybersex (cybersex: Virtual (as in, not in person) sexual experiences or encounters which involve text conversations and/or visual exchanges via the Internet.) , mutual masturbation (mutual masturbation: When sexual partners masturbate together. Sometimes people also use “mutual masturbation” to mean manual sex (fingering or handjobs) done at the same time.) , masturbation (masturbation: Ways that people seek out and/or experience sexual pleasure by themselves, without a sexual partner.) …and just about anything else you can dream up in which one or more than one person is doing something seeking or experiencing sexual gratification.
And how any one person or more does those given activities also varies: by position, by how people are touching each other, what body parts come into play, the works. Sex between people is basically improvisational dance: how two people do something is (and should be) about what feels good to both of them, with their unique bodies and preferences, and how both uniquely work together.
So, in short, you asked a much bigger question than you perhaps meant to ask. Your best bet? Peek around the whole site here if you’re thinking about one particular sexual activity. Experiment with and talk with your partner (partner: In a sexual context, a person with whom someone is having some kind of sex. The term “partner” can be used for all kinds of relationships, not just serious ones. “Partner” can also mean the person someone is with in a romantic or familial partnership.) – after all, as a people, we’ve figured out (out: Short for ‘out of the closet’. When someone’s LGBTQ+ identity is known to other people.) the basic mechanics of these activities before we could even read, the mechanics really are pretty intuitive and uncomplicated. Explore, and ENJOY the exploring: that’s one of the best parts!