Fill out the form on the front page to Sign Up, then you should see this screen:
Choose "Freenode" from the dropdown
Put in an all one word nickname to use on irc (think of it as a username), you can put in a real name if you want, but you don't have to, and you can go ahead and list any channels you want to join. Click "Join network"
A whole bunch of esoteric dork stuff will happen on the screen, but EVENTUALLY you should see something like the screen above, where you can talk in the channel you set it to join.
There are a LOT more resources out there. A pretty simple one. One that is teaching me stuff I don't know about chanserv.