IRC is Internet Relay CHat
You connect to a chat server. I only been to wincustomize room once and don't remember the address. But it would be something like chat.wincustomize.com port 6667
You put a chat name in the nickname and in user info put guess who or some other stupid thing so chatters that do a check on who you are don't find diddly.
Some servers require a real email address or a password but they are few and far between. Mostly those servers that are plagued by script kiddies that flood rooms.
Once you connect to a server type /list and when the room list comes up pick one you like and double click it.
Once your in the room jump in and start chatting.
Many new chatters are scared to jump in and that is a big mistake. Most chat rooms don't like lurkers and it is better to say you are new and you will get flooded with hints, and suggestions to make it easier.