There are better game clients available to use, and here is a walkthrough on how to get and use one, it is really simple.
Need more detail, read on:
Once you have chosen a name for your character you can start playing 4D using the basic telnet application. Follow the directions and in no time you'll be walking around in the exciting worlds of 4D. Or you can first visit our Getting Started Page.
Do you have a MUD client already?
4Dimensions accessed from your own mud client with these details 4dimensions.org port 6000.