First, go to Pidgin's website, and download the client for whatever OS you are using.
For this guide, I will assume you know how to install software. If not, then let me know, and I'll revise this to include installation.
After the program is installed, run it.
It will probably tell you that you have no accounts set up, and it will let you create one, etc, but close that welcome window.
Your screen should look like this.
Go to the "Accounts" menu, and pick "Manage"
You will be presented with this screen, showing that you have no accounts set up. Click "Add"
Next, pick the account type. Pidgin supports like 20 different client technologies, and if you want to set it up to work with your AIM, Yahoo, MSN, etc, then this guide applies to that too (up to this point). Choose "IRC" from the dropdown list.
Next, we will set up IRC to talk to the server that hosts the ADISC channel.
The only thing that really matters here is that you set the server to "irc.blitzed.org". Aside from that, you can pick whatever screen name, etc you want.
A password is not required.
Setup on the "Basic" tab.
Setup on the "Advanced" tab.
After you set these options click "Save". This should enable your account. It may take a minute to connect to the IRC server. When it does, it will probably pop a window up with a few messages from the server itself.
If you want, you can just type "/join #adisc" and you will be connected into the ADISC channel.
You can also set up the chat so that you can join it just by clicking on it.
Click on "Buddies", then "Join A Chat"
Pick your newly-created IRC account, and in the channel box, type in "#adisc"
This should connect you right into the ADISC channel.
If anyone has any trouble with this guide, let me know. I'd be glad to help you figure it out.