Have you read this sticky here? :-
http://www.racedepartment.com/threads/a-guide-to-our-leagues-on-racedepartment.93394/
But essentially you go to the league forum and pick a PS3 league you are interested in. Go into that league's sub-forum and read their sticky threads, which will contain their rules, racing calender, and a sign-up thread.
If you want to join that league you post in the
sign-up thread that you want to join their league. This will depend on whether they have spare slots available for a driver. There is a maximum amount of players that can be hosted in one session. You are committing to turn up every week and race, it's a racing league not random game that you can just join online when you feel like it.
You are expected to comply with their racing rules and RD's racing rules (driver etiquette). Some leagues
may require you to have an RD racing licence (free). There is no need for this RD licence generally for Codemasters games, because RD does not host the servers for these games, as the games have no dedicated servers.
Assuming that your application is accepted. One of the drivers will host the race, often the one with the best connection. The rest of the racers in that league will then join his privately hosted race.
If you ever need to apply for an RD licence, the general rules are here, with a link to the licence application thread.
http://www.racedepartment.com/threads/read-this-first.43576/
Sound complicated but it isn't really
Good luck and have fun
