Walk through the Toast module in React Native

I am very new to react native. I need to use a pure native SDK provided by external source in a React Native Application. This is the link I found(the toast example).

https://facebook.github.io/react-native/docs/native-modules-android.html

I have gone through the documentation but I really don't get it. Can someone walk through the Toast module specifying what really needs to be written where in the default project structure of react native that is created using react-native init "ProjectName"?