Well, generally there are three ways. Politically, economically, and by force. Politically, you rise to a position of power, and then from there convince other people in other positions of power to give you control, thus increasing your power. In due time, you would have power over the entire Earth. This would require convincing other world leaders to give you command over their country. Economically, you would become the richest man on the planet, and then with that money you would start buying up all the land on the planet. You would buy entire countries. Not even Bill Gates has enough to do this though, not by a long shot, he has such a small fraction of the amount needed. And by force would require building up an army, and conquering lands. If you want people to join you though, you need a good vision to sway people to your cause. You need to be a visionary.