Instructions
Select "PlayStation Network" from the main PS3 screen, then choose "Account Management."
Scroll down until you see "Facebook," then press "X" for more options.
Highlight "Publish Trophy Stories," "Publish Purchase Stories," "Publish Game Event Stories" and "Allow access from games," then press "X" to toggle each option to "On." The system prompts you for your Facebook username and password.
Enter your Facebook username and password to complete the linking process. From now on, updates about what games you are playing and any trophies earned are posted automatically to your Facebook wall.