Update user guide with Android instructions.

Author: anp

react-native-scripts/template/README.md

@@ -55,7 +55,10 @@ Like `npm start`, but also attempts to open your app in the iOS Simulator if you
 
 #### `npm run android`
 
-Like `npm start`, but also attempts to open your app on a connected Android device or emulator. Requires an installation of Android build tools (see [React Native docs](https://facebook.github.io/react-native/docs/getting-started.html) for detailed setup).
+Like `npm start`, but also attempts to open your app on a connected Android device or emulator. Requires an installation of Android build tools (see [React Native docs](https://facebook.github.io/react-native/docs/getting-started.html) for detailed setup). We also recommend installing Genymotion as your Android emulator. Once you've finished setting up the native build environment:
+
+1. Make sure that you can run adb from your terminal.
+2. Open Genymotion and navigate to `Settings -> ADB`. Select “Use custom Android SDK tools” and update with your [Android SDK directory](https://stackoverflow.com/questions/25176594/android-sdk-location).
 
 #### `npm run eject`