[Docs] Explain navigating between screens in Navigation Guide

docs/Navigation.md

@@ -30,6 +30,7 @@ npm install --save react-navigation
 Then you can quickly create an app with a home screen and a profile screen:
 
 ```
+/* from App.js */
 import {
   StackNavigator,
 } from 'react-navigation';
@@ -39,11 +40,30 @@ const App = StackNavigator({
   Profile: { screen: ProfileScreen },
 });
 ```
+Now we need HomeScreen and ProfileScreen components to be imported. We will be making these two components in a separate folder `components` in root dir.
+After importing StackNavigator from react-navigation module and screens from `components` folder your `App.js` file will be:
+```
+import React from 'react';
+import { StackNavigator } from 'react-navigation';
+import HomeScreen from './components/HomeScreen';
+import ProfileScreen from './components/ProfileScreen';
+
+const App = StackNavigator({
+  Home: { screen: HomeScreen },
+  Profile: { screen: ProfileScreen }
+});
+
+export default App;
+```
 
 Each screen component can set navigation options such as the header title. It can use action creators on the `navigation` prop to link to other screens:
 
 ```
-class HomeScreen extends React.Component {
+/* from ./components/HomeScreen.js */
+import React from 'react';
+import { Button } from 'react-native';
+
+export default class HomeScreen extends React.Component {
   static navigationOptions = {
     title: 'Welcome',
   };
@@ -60,6 +80,22 @@ class HomeScreen extends React.Component {
   }
 }
 ```
+Now it's time to jump to Profile Screen
+```
+/* from ./components/ProfileScreen.js */
+import React from 'react';
+import { Text } from 'react-native';
+
+export default class ProfileScreen extends React.Component {
+  static navigationOptions = {
+    title: 'Profile',
+  };
+  render(){
+    const { state } = this.props.navigation;
+    return <Text>Hello, {state.params.name}!</Text>
+  }
+}
+```
 
 React Navigation routers make it easy to override navigation logic or integrate it into redux. Because routers can be nested inside each other, developers can override navigation logic for one area of the app without making widespread changes.