facebook.github.io/react-native/
github.com/jondot/awesome-react-native
Is good place to start.
If you know React Js and concepts you already know most of the React Native. Their are few custom styled elements similar to HTML elements that gets converted to native elements when rendered, and some js based over the top API's to consume Android API's.
Their is some extra setup required to run android apps during development, all details are on react-native official website.