Hey Epsy, you have to be a premium member in order to join the race.
Just to tell you - it is very much worth the very modest fee for a year. There are races ever week (almost every day really) and the drivers taking part in these are all top blokes.
There is good competition for every skill and races are always good fun. You will find a very well mixed field in these RD club races from blistering fast aliens through very fast and ambitious midfield competitors to relaxed gentleman racers who enjoy that ride to complete green behind the ears freshmen. All are equally welcome.
There is a lot of camaraderie with everyone just helping out. No public server crash kids around here ;-)
Sign up for premium, make sure to set your real name in the account settings here in the forum (there is a feature that only premium members will be able to see your real name if you use the correct field), set your real name in TeamSpeak and Assetto Corsa so the moderators of the racing event are able to verify that it is you, read the introductory post in the thread to familiarize yourself with the rules passwords and general procedures during the event and be sure to check out the practice server as well to get a few laps under your belt before committing to race.
Once you have signed up it is always encouraged to show up early on the server - usually the practice server for each event stays online until the actual race server is opened and people always shop up a little early, practice together before the actual event practice session starts and have a chat, help out with issues, …
I am sure I speak for everyone that you won't regret it and you will be welcome ;-)
+ another participant with a good taste in cars is always needed ;-)