This applet will connect you to irc.synirc.net and will automatically join #pharyngula. If you are not registered with NickServ on that network, ask people in the channel for information on how to do that (and on why you should do that, if you're unsure).
It is advised that you get a real IRC client (like mIRC, if you're a Windows user). This applet is really only here for people on weird OSes and/or computers on which they cannot install software.