You can now challenge your Facebook friends to a game of chess which is now possible on Facebook messenger. To start, all you need do is drop the following lines into your conversation “@fbchess play”
That's it, though. If you're having a little trouble playing the game or deciphering the commands, type “@fbchess help” into your chat window and Facebook will come to your aid.
You can also send a few other commands to @fbchess. If you're getting demolished, just add "resign" to your message to tip over your virtual king. If you're curious how you've been doing, "stats" gives you a little rundown of your efforts so far. You can also pick what colour you want when you start playing if you're the person who initiates the game—remember, white plays first.
As Lifehacker notes, you can also click on the chat menu settings icon and select the option to "See Full Conversation" if you want to play on a larger chess board.
source http://www.timigate.com/2016/02/how-to-play-chess-on-facebook.html#more