
Anyway, I don't know what your specific problem is, but I'll try to take you through all the steps. Corrections to these are welcome; I got it to work without exactly understanding what everything means. (I guess I have a bit of Slylandro in me.)
1. Go to the "Trillian" menu and open "Trillian Preferences..."
2. Select "Plugins." Is the IRC Plugin installed? If not, install it. If it is...
3. Select "Identities and Connections." Click the "Add a new connection" button and select "IRC."
4. There are 5 fields to fill in:
-- Connection Name (I think that's what it's called): This can be anything you want. It can be your user name. I called it "Ur-Quan Masters."
-- Connection and Port: Type in irc.freenode.org::6667 (I don't know why 6667, but that's the default and it works)
-- Nickname: This is the user name other people will see when you post on IRC. You can change it at any time by typing "/nick newname"
-- Username: This is your actual user name for IRC. No reason for this to be different from "Nickname," really.
-- User Info: Optional
5. Use the check box to choose whether you want to "Automatically connect to this account at startup." If you don't, you can connect by following step 6:
6. Click the "Connect" button to connect to IRC, then close the Trillian Preferences window.
7. Now you should be connected to IRC (the white circle in the Trillian window ought to be lit up), but nothing will happen unless you join a channel. Click on the white circle to bring up a menu, then select "Join a Channel..."
8. Type #uqm-arena in the window that appears. That should work!
I hope that helps. If you have a problem, tell me which step it comes on.