With CRNA, all you need to do is to install node and npm on your computer. Then, install the CRNA command line tools:
$ npm i -g create-react-native-app
To create a project named HelloWorld, use the following command:
$ create-react-native-app HelloWorld
$ cd HelloWorld
You would develop the app just like a normal React Native app. When you are ready to test the app, simply use this command:
$ npm start
A barcode that is unique to your app will now be generated.
That's it! To view your app, download the Expo Client app on your iPhone or Android device. Scan the barcode unique to your project and voila, your app now runs on your iPhone or Android.
I think this is the coolest way to learn iOS and Android programming!