If you'd like to make iChat your client for connecting to MSN, Yahoo! Messenger, or Jabber, there's a few more steps you'll need to follow. Let's start with Jabber in general.
To allow iChat to connect to a certain client, you'll need to create a Jabber account since iChat doesn't natively communicate with MSN's services and servers. To create a Jabber account, first choose a server that supports the client you're connecting to (i.e. MSN, Yahoo!, etc) in this list by Jabber.org. Click on the link for that server and create an account on their network which is free in most cases. It's preferable that you choose a server that's close to your location and at the same time offers the server you want to connect to (i.e. MSN, Yahoo!, etc). This isn't always possible though; in that case, just pick a server that pleases you.
The reason for picking a server close to you is because of latency, or how far the signal sent needs to go to connect to the server and then back to you. Obviously the further away the server location, the more latency and possible slow response. Choosing a server in your country will also likely mean that their instructions for setting up Jabber will be in your native language, which is always an advantage.
Once your account on that server is setup, you'll be given a server to connect to, in addition to your username and password to connect to that server. Under Preferences > Accounts, click the "+" sign to add a Jabber user to your iChat client. It will look like the following:
Still in need of assistance or help in setting up iChatAV? Check out these links:
Are you looking for someone to test your video/audio connection with? My screenname is available normally 24/7 and is iChatAVTesting on AIM. Please note that this is an unmonitored account and all IM's will NOT get a response. In addition, be courteous of other users who use the screenname. See the profile of that account for the latest information. I ask that you don't stay connected for more than a few minutes due to the fact that you are using my bandwidth, connection, and other users' opportunities to test. There are also other iChatAV users willing to test your connection with you around the world. They are listed here.
Enjoy!
MORE TO COME AT A LATER DATE