Android simulators are launched in the same way as the iOS simulators. In the terminal where the React Native packager is running, press "A". However, there's a caveat - you have to start the Android device emulator before starting the app within the React Native package. If you don't, you'll see a message that looks like this when you press "A":
2:37:02 p.m.: Starting Android...Error running adb: No Android device found.
This has been historically difficult to do with Android. Getting Android device emulators up and running is much simpler now, with the help of Android Studio. Once you have Android Studio installed, you can open the Android Virtual Device manager and add any device you like:
You can click on the Create ...