The lottery process is for returning students (rising sophomores, juniors, seniors). Incoming freshmen do not have to worry about this. You should have received a housing preference form as an incoming freshman – this is a first forms received, first preference process.
RPI does not assign the halls. Students are entered in the lottery (you have to sign up for the lottery as an upperclass student). ResLife randomly assigns lottery numbers. Students choose their room based off of the numbers. This is a really simple breakdown of a more complicated process, but you do not need to worry about this for another year.