Ok, so you want to join the IRC (Internet Relay Chat) community? First off, you need a client. There are many available for Windows/Linux/Mac - some are open-source - some are free - some are not. Basically, take your pick, but here's a list of the more commonly used clients.
This tutorial is specific to the default IOL supplied Router/Modem - Zyxel Prestige 600, however it can be modified for other setups as many routers and modems have similar options. Look at this if you are having difficulty setting up a server when behind one of these devices