If you have already signed up for the beta, you will automatically receive the updated version of the application through the Google Play Store.
If you have not signed up for the beta and want to partake in it,
- Join the Facebook for Android Beta Testers Google group:http://bit.ly/FBAndroidbeta
- Tap Become a Tester in the Google Play Store and download the latest version of Facebook: http://bit.ly/121po70
[UPDATE] The Facebook 3.9 beta for Android has been updated (10/29/2013) with the following new fixes and improvements:
- Fixed a crash when starting up
- Fixed a crash when viewing news feed
- Various additional bug and crash fixes