I can't speak for MIT as I'm from Purdue, but as I understand it the process is basically the same as it would be for a person from this country. Universities typically divide tuition fees into two categories, in-state and out-of-state. You would fall into the later category, simple enough. As for being from outside the country you are more likely than others to get accepted to the school as they are always striving for a diverse student body. Simply put, you should just apply and see what they say. If you have really good grades and SAT or ACT scores you should be fine, despite the fact that MIT is a very competitive school.
MIT is a university, not an organization. You don't 'join' it. You apply to it like any other schools. Admissions information is on their website.
MIT is a private university. They don't care what state or country you live in; tuition is the same. Applying from out of the country lowers your odds of admission. Everyone applying has the highest grades in the hardest classes and very high test scores; they turn down more than 90% of these applicants. You need a lot more than that.