Linking your Facebook account with your Twitter account will make it even easier for you to share your thoughts with your friends and followers. If you want to know how to do it in just a few easy steps, follow these instructions.
1. Visit www.facebook.com/twitter.
2. Click on "Link my Profile to Twitter."
3. Click on "Authorize app." This will allow your Facebook account to post to your Twitter account.
4. Make any necessary adjustments to your settings. You should be told that your Twitter is now linked to your Facebook profile. Right now, there will be checked boxes next to the following: status updates, photos, notes, videos, links, and events. If you'd like any of those to not be linked to your Twitter, then you can unclick them and select "Save changes."
Borrowed from: http://www.wikihow.com/Link-Facebook-to-Twitter.
Borrowed from: http://www.wikihow.com/Link-Facebook-to-Twitter.