If a PC which is not already registered to use a particular network is connected to that network, you should be able to register that PC by following a step by step procedure. Just open the web browser, go to any site, and the registration system should appear.
While the system has been extensively tested, it is almost inevitable that there will be at least some teething problems with a system as complex as this. If you experience problems using the registration system, please report the problem to the helpdesk. E-mail support@ru.ac.za, and please be sure to include your username, the exact text of any error message that you see, the MAC address of the PC, and the building which you're trying to register your PC for. The name & version of your web browser (e.g. IE7) may also be useful..