FIFA member countries (even countries together) can submit a bid for the World Cup, and then a bunch of FIFA officials (about 22 to 24) get to vote, and as soon as one bid gets a majority in votes they get the World Cup. If after a round of voting one bid doesn't have a majority then the bid with the lowest amount of votes (England for 2018, Australia for 2022 for example) can't be voted on again in round 2.
As you can see it's really easy to buy a World Cup since you only need to buy about 12 or 13 votes, which especially for rich governments like Russia's and Qatar's isn't a problem.
ahhh, ok. That clears a lot up. Thank you!