Here are the basic steps for set up and use:
First, download the notifier from here (don’t bookmark that for when/if it chagnes) and place it somewhere you don’t mind it being since the file isn’t an installer, it’s the actual program. (Basically just don’t save it to the desktop or you’ll probably put it in the Recycle Bin at some point).
After it’s downloaded double click it to start it. It should bring you up to the imo.im front page while running down in your system tray.
Double click that tray icon to hide or show the window.
If you want the tray notification to run at start up, right click on it and go to “Options”
(If you want to stop it starting with windows at any point, click on that again and choose “No”)
The options also allow you to start up in the thin mode as well.
Once it’s running you should see the icon change when you have waiting messages. Again, double click the system tray icon to bring up the instant messenger window.