The IS Boxer wizard should leave you with a default functional interface.

Simply drag the Lightning bolt from the spell book onto hotkey 1.
Do the same for other other toons.

And when you press 1, each of the toons should auto assist whichever window you are in, and each cast/use whatever ability is on hotkey 1.

If you haven't done much configuration/tinkering around.
I'd recommend wiping your configuration for IS Boxer.
And then running the wizard again from scratch.

You can also paste your configuration via pastebin.
The IRC is probably the best place for support, but this thread works too.
http://www.lavishsoft.com/chat/isboxer.php