You need an irc client. The more popular options are:Edited By: Alister Jacobs on Year 10 Day 66 23:21
ChatZilla extension for firefox - https://addons.mozilla.org/en-US/firefox/addon/16
XChat (install from Application -> Add/Remove programs)
Pidgin can handle IRC. It is installed by default.
In the first two cases, install and start the client, then the usual irc commands will work ( /server irc.swcombine.com and then /join #swc-members ). Pidgin needs you to add an account (accounts -> manage accounts -> add) with the server irc.swcombine.com
The Combine Java applet will probably work too. If it doesn't, you might like to install java (I'd recommend using the instructions at http://tombuntu.com/index.php/2008/04/25/10-tips-for-after-you-install-or-upgrade-ubuntu/ point two, and consider all the points as things you might like do).