Base IRC Commands:
/nick changes your nickname
Example: /nick newnickname (limit 9 characters)

/msg nickname nickname (message) to start a private chat..
Example: /msg puddytat Hey tat, how are you?

/quit to leave IRC altogether. This disconnects irc from the server.
Example: /quit Going out for dinner...nite all!

More information in:

Chat Support

Note: if you can't see the chat ensure you have installed Java Plug-in, then look at the Java Control Panel (right click on the systray icon) and check if Java is active on your browser.

Download Java Plugin