To begin you first need to download a irc program, I've listed some here:

Visual IRC For PC's *I use this one*
Mirc For PC's
Pirch For PC's
ircle For Mac
Amirc For Amiga

One other thing you should consider is protecting yourself and system from Nuke attacks. A nuke is the process of taking you off the Internet and/or locking up your computer, through bugs in the internet protcols. It doesn't just affect you in IRC, although it is the most common place for this to occur. This is because your IP is so accesable. To make nuke attacks less likely you should go to Nuke Patches and download all the patches. Be sure to follow all the directions carefully.

Now that you have everything up and running you are ready to begin IRC. To do this you simply start the program, select a server and connect. Once in IRC land there are a number of commands You need to know to get around.
The Basic Commands are:

/join #channel

This command allows the user to join a channel. Example of this is as follows "/join #irchelp" this command would make me join #irchelp. All channels start with the # sign.

/leave

This command exits the user from the channel. I would type this if I wanted to leave channel #irchelp.

/nick desired_nick

This command allows you the ability to change your nick. Example is "/nick bob" would make me known as bob.

/msg nick

This command allows you to privately send a message to a user on IRC.

Xcalibre
Mirxc
Hawkee

Small Bug in IRCN:
The bug is not only in ircN It is in mIRC.
The problem is $calc(..)

ircN is just one of the scripts who use $calc to check the ping delay
eg:

on 1:CTCPREPLY:PING*: { echo -a Ping reply: $calc($ctime - $2) }

To protect yourself, add this to your script:

on 1:CTCPREPLY:PING*: { if ($2 !isnum) { halt } }