Hi,
did you download and install the "Autoupdater" already?
You can find it here if you haven´t already installed it:
Autoupdater
If you wait until the Autoupdater finished its work with downloading and installing all the cars and tracks automatically (you only need to install the Autoupdater for the games you want to play with us!), you need to download the
Lobby-Patch extract the files and copy all three of them into your main GTR2-folder (i.e. .../Games/GTR2).
Once you´re finished with that, you should be able to join the servers in the lobby. And don´t worry if you´re kicked from the server because of "cheating suspicion" (don´t know the perfect english term GTR2 uses) - that happens from time to time and you should just try it again. If this happens too often or you have other problems, just ask.