I'm sure that I'm missing something obvious in plain sight, but I can't find it anywhere... How do I set up the Instant Messaging to work? And then how do I log in to it via Gaim/Pidgin?

Here's what I've tried so far:
1) Make sure that in the default COS (which covers EVERYONE), IM is checked in the major features.

2) In a regular Zimbra client I can see "new:chat" and I can tell it that I want to talk to someone else who's logged in, but then I'm dead after that. I can type into the chat window, but hitting return does nothing. nada, zip zilch.

3) Thinking that the problem might be in the client, I experimented with hooking in through GAIM with best guesses for settings. my account login, my password, the zimbra server's addy in the server spot... GAIM says that it can't reach the server.

I'm wondering if maybe we didn't enable something we were supposed to have at install time? But, I haven't found any mention of IM in the documentation at all except as a note in the release notes that it exists, so I'm at a complete loss.