Multiple clients on Android IM application

For the last four hours I have been trying to get the G1’s IM client to add another account. I’m using my main Mobile Industry Review account on the device — but I have a load of other accounts that I’d like to use — MSN, Yahoo and so on — but I can’t for the life of me work out how to add them.

It appears to be possible judging by the screenshot of the video posted by the Google Android IM/Gtalk team.

I can’t find a How-To or a manual for this… has anyone figured it out?