Get one of the common IRC programs available and go through the setup and you should be able to get going in short notice. Once you've got connected to a server, and listed the channels, and decided on which one to join, consider these bits of advice. The servers that run IRC are all over the world. Because of distance and the amount of processing that needs to be done to relay the chat lines, there may be some lag between the time you write something and someone else reads it, and vice versa. Also remember that the other folks may not see a need to reply to your every line.
Some channels are just slow, well relaxed.
Some others are, well, chaotic. For those, continue reading for other tips. If it's supposed to be fun, then, obviously irates are not going to be welcome. Except for the perversion channels, most of the people on IRC are friends, want friendship, or want to be friends. Don't expect everyone to speak at once.