I don’t know if this is really what you need but, did you go on the react-native documentation and click on the tab “React Native CLI Quickstart”?
For environment setup → Setting up the development environment · React Native
For publishing:
Android → Publishing to Google Play Store · React Native
iOS → Guides (iOS) from the left navigation panel?
I followed environment setup for android and I installed and configured the react-native-unimodules package but I’m stuck because the build doesn’t work when I npx react-native run-android (See my post here).
If you’re talking about a release build, perhaps my answer doesn’t fit your needs 
. If you have anything to help me I would appreciate 