The whole formality of asking to be in a relationship or asking someone if they will be your girlfriend/boyfriend doesn't even happen. You hang out, you go on a date or two or three, physical stuff more often than not happens, and at that point, not depending on physical stuff, you are already in a relationship. There's no contract or formal agreement.
Again I stress the point that sex does not have to happen in order to be in a relationship.
I'm stressing that point seeing as you've never been in a relationship and don't know how they work so I assume you would believe anything a potential boyfriend would tell you to get in your pants, assuming again he's a dickhead.