Once you turn on text messaging, the texts you exchange with friends are incorporated into your conversations along with your message and chat history. This allows you and your friends to message each other even when you’re not at your computers.
Getting and responding to messages from your phone
Once you turn on text messaging, friends can check the "Send to Phone" option when they send you messages. If a friend checks this box, you’ll receive a text that contains the message. Simply reply to the text from your phone, and your friend will receive your reply as a Facebook message. It will also be logged in the ongoing conversation with your friend, which you can view from your Messages home page.
Sending messages from your phone
To send a new message to a friend via a mobile text, just text the following to 32665 (FBOOK):
msg john smith what’s up?
This would send the message "what's up?" to your friend John Smith.
Controlling text notifications
You can control which text notifications you receive on the Notifications tab of your Account Settings page.