Getting Started with Android Devices
Step 1. Prerequisites
Follow the getting started guide for login on Android.
Step 2. Enable Login for Devices
Load your app's dashboard and change Products / Facebook Login -> Settings > Login from Devices to 'Yes'.
In your app's strings.xml, make sure you also have an entry for client_token set to the value in your app dashboard under Settings -> Advanced > Client Token (this should be next to where you set the app_id in your string.xml file).