1. Follow the instructions on the "React Native CLI Quickstart" tab of the React Native setup instructions. These instructions fan out by host operating system (macOS, Windows, Linux) and target operating system (iOS, Android). Follow whichever is appropriate.

2. Install the Javascript dependencies

   yarn install
   

3. Install iOS dependencies (iOS only)

   cd ios
   pod install
   

Start an emulator or plug in your device, then:

yarn run android

If running on a device you must first:

1. Enable USB Debugging on the device
2. Run adb reverse tcp:8081 tcp:8081 at the command line

yarn run ios

This will start a simulator for you.