You get an initial rating by playing a number of tournament games against rated opponents.
The results of every rated game (played at tournaments etc) are reported to a rating body. Back when I played (low level) competitively, rating lists were published every couple of months in paper form; nowadays it's all online, of course.
The results of every rated game (played at tournaments etc) are reported to a rating body. Back when I played (low level) competitively, rating lists were published every couple of months in paper form; nowadays it's all online, of course.