HOW TO ACCESS FACEBOOK CHAT FROM YOUR DESKTOP
Facebook's built-in Messenger is a fun way to chat with friends, but tying up your browser with it is a little annoying. Fortunately, you have the option of using a regular chat program instead.
First, you'll need an IM client that supports Jabber/XMPP messaging. iChat, Pidgin, and Adium will all work.
Fire up your chat program of choice. Find the "Accounts" option, then click "Manage" and create a new account.
If you're using Pidgin or iChat, you'll have to select either Jabber or XMPP as the account type. Adium users can just pick "Facebook."
Type your Facebook profile ID and password. To get the profile ID, open your Facebook page and click the Home button at the top. Then look at the Web address. The profile ID is whatever comes after "www.facebook.com/".
For example, mine would be "kim.komando". If you never set your name, it might say, "profile.php?id=123456". You want to use the number that comes after "id=".
If you're using Pidgin, there's a few extra steps to take. Where it says "domain" type in "chat.facebook.com" and for "local alias" type in your name as it appears in your Facebook profile. Now click the Advanced tab and for "port" enter 5222 and for "connect server" type in "chat.facebook.com". You should be set.