If you have an IRC client and know how to use it:
That's great. The party is in #ubuntu-california on irc.freenode.net. You should be able to find your way.
If you want an IRC client:
There are several IRC clients. The major ones are XChat for linux (not to be confused with xchat-gnome. Don't get that.) and mIRC for Windows. If you have pidgin, that can also be co-opted to do IRC, but keep in mind that it's not entirely meant for that. To learn how to use it, consult your client's (whichever one you choose) documentation. Then go to #ubuntu-california on irc.freenode.net. If you don't feel like doing it, just type in the text box:
/connect irc.freenode.netThose are two separate lines. Those commands will get you there no matter what client you use.
If you don't want to install an IRC client, but still want to attend:
You can use a web-based client, this Java applet one is one that I recommend, and is one that I survived on in Arizona. It's best for just dropping in temporarily. If you wish to remain in IRC, it's highly recommended that you use a client.
If you want to do it the 1337 |-|aXX0r way:
If absolutely desired, I may allow you to ssh into my machine and use irssi (a text-based client) to join. If you would like to do this, contact me. I'm not putting my machine stats on the internet. And it'll help if I actually KNOW you. This method is highly discouraged.