/part #channel_name
Leaves the channel named #channel_name
/join #channel_name Enters the channel named #channel_name
/nick penguin
Changes your nickname to "penguin"
/whois penguin
Shows information for the nickname "penguin"
/privmsg penguin hi!
Sends "hi!" privately to "penguin"
To talk on the channel just type what you want them to see and hit the enter key.