Hello and welcome to PR mate. Have you installed the latest version of Project Reality (1.4.1.0)? If not, you can download it from
the Downloads page of this website.
If you have it installed already, you should start PR by the PR Launcher shortcut on your desktop where it will ask you to create an account. Once you're done with that, you can adjust your video and audio settings as well as your controls through the launcher or you can just click Play and the game will start up. Once in the game, hit Deployment and then Join Internet. You should be able to see the servers.
The game might ask you to let it through firewall so make sure that you click Allow if the dialog shows up.