We can't document all of them. We don't have time. If your personal favorite client is not on our documented list, it can probably still work. CS Chat uses something that used to be called "Jabber", but has been since renamed to "XMPP". If your client supports either of those names, you can use it to connect.
Create a new account in your client, using your Customers Suck! screen name (replacing all characters that are not numbers or upper/lower case A-Z with _ characters). The server or domain will be cschatter.com. Your password will be exactly the same as you have used for the forum. If your client asks you for a "resource", set that to be your screen name + the name of your IM client.
From there, you will be able to connect up and use CS Chat. To join the main group chat room, find the option in your program that says to join a group chat, or a multi-user conference, or something similar. The address to plug in will be "firstname.lastname@example.org". Some programs do not allow you to change your nickname once you join a groupchat, so make sure to specify the nickname you wish to use before clicking the join button.