In this tutorial I'm assuming that you already have Pidgin installed ( if not go to http://www.pidgin.im and install it ).
Once you've got it installed you'll need a username and password. Your password currently may not have special characters in it. That part is pretty easy.
To figure out your username, it's your forums name all lowercase and replace spaces with _ ( ' with - ). Your password is also the same as your FCON Forums password. If it tells you that it cannot find your username then it will tell you what you need to do in order to get one.