You can find the latest versions of the Facebook apps by going to the Facebook for Mobile page or visiting your phone's app store (ex: iTunes App Store, Google Play). From here, you can see what's new with the app and install the latest version.
First, make sure you have the most up-to-date version of the Facebook for Android app.
To update your app:
1. Go to the Play Store
2. If there's a newer version of the Facebook app you don't have yet, it'll be listed there for you to download
If this doesn't resolve your issue, let us know.