These step by step instructions set up Facebook so that any posts you make to Facebook will also appear in / are synced to Twitter.
1. Go to http://www.facebook.com/twitter/
2. Click on ‘Link a Page to Twitter’
3. Click on ‘Link to Twitter’
4. Oddly, nothing happens… Or does it? Look carefully and you will notice that the URL in the browser bar has changed. Copy that URL and paste it into a new browser.
5. Click on ‘Allow’ to allow your Facebook account to post to your twitter account: ‘brwilson71’ in my case.
6. Congratulations. You are now sharing your Facebook updates on twitter. Don’t forget, updates made to Facebook that get posted to Twitter may be seen by everyone.
Also, see how to link Twitter to Facebook.