Try these instructions
Google Talk = Google's new IM service that they're announcing tomorrow.
All you need is a Jabber-compatible Instant Messaging client (such as Apple's iChat, or GAIM), and a GMail address. Digg this, NOW!
WELCOME SLASHDOT and DIGG USERS!
If you're getting the 405 error with GAIM, or simply cannot connect anymore, follow the updated configuration instructions below!!! You have to use an @gmail.com address to login from now on.
Google's offical client has been released, as expected. Download here for Window only. Mac/Linux, or Windows rebels, keep reading below.
Server: talk.google.com
Username: youremail@gmail.com
Password: yourpassword
Note: If you can't login, try to turn off 'Secure Messaging' or 'Encryption'... etc.
-- TRILLIAN USERS: Someone just told me that they got it working with Trillian, but I can't verify this. Just go to Trillian's plugin page on their site and download the Jabber plug-in, install it, and configure a new connection as below:
"server : talk.google.com
port : 5222
Use legact SSL for connection : not checked"
How to set it up with GAIM on Windows/Linux, or Adium on the Mac:
-- For iChat, just enter the information above.
1. Add an account, select "Jabber" as the protocol.
2. Your screen name is everything before the '@gmail.com'.
3. Server is 'gmail.com'.
4. Click "show more options" and make sure "use TLS if available" is checked. Leave "Force old SSL" and "allow plaintext..." unchecked for now. Connection port should be 5222, connection server should be 'talk.google.com' without the quotes.
5. Ta-da! Just login and you should be good-to-go.
Another user reports the following:
"weird, I've never sent you email from my gmail, and now that you're on my buddy list on google talk, it autofilled your email address, and alias on my gmail"
-- The "/me" command works too, even on iChat. "/me says hi" translates to "smash says hi" or whatever if you're not familiar!
Instructions are the work of Ben Guild (Smash)
www.smashsworld.com/