improve README.md

Author: rwieruch

README.md

@@ -49,15 +49,55 @@ If you are creating an open source application under a license compatible with t
 * `cd react-redux-firebase-authentication`
 * `npm install`
 * `npm start`
-* visit http://localhost:3000/
-* Use your own Firebase Credentials
-
-### Use your own Firebase Credentials
-
-* visit https://firebase.google.com and create a Firebase App
-* copy and paste your Credentials from your Firebase App into *src/components/Firebase/firebase.js* file or in .env file
-* [activate Sign-In Methods in your Firebase App](https://www.robinwieruch.de/react-firebase-social-login/)
- * Email/Password
- * Google
- * Facebook
- * Twitter
+* visit http://localhost:3000
+
+Get an overview of Firebase, how to create a project, what kind of features Firebase offers, and how to navigate through the Firebase project dashboard in this [visual tutorial for Firebase](https://www.robinwieruch.de/firebase-tutorial/).
+
+### Firebase Configuration
+
+* copy/paste your configuration from your Firebase project's dashboard into one of these files
+ * *src/components/Firebase/firebase.js* file
+ * *.env* file
+ * *.env.development* and *.env.production* files
+
+The *.env* or *.env.development* and *.env.production* files could look like the following then:
+
+```
+REACT_APP_API_KEY=AIzaSyBtxZ3phPeXcsZsRTySIXa7n33NtQ
+REACT_APP_AUTH_DOMAIN=react-firebase-s2233d64f8.firebaseapp.com
+REACT_APP_DATABASE_URL=https://react-firebase-s2233d64f8.firebaseio.com
+REACT_APP_PROJECT_ID=react-firebase-s2233d64f8
+REACT_APP_STORAGE_BUCKET=react-firebase-s2233d64f8.appspot.com
+REACT_APP_MESSAGING_SENDER_ID=701928454501
+```
+
+### Activate Sign-In Methods
+
+![firebase-enable-google-social-login_640](https://user-images.githubusercontent.com/2479967/49687774-e0a31e80-fb42-11e8-9d8a-4b4c794134e6.jpg)
+
+* Email/Password
+* [Google](https://www.robinwieruch.de/react-firebase-social-login/)
+* [Facebook](https://www.robinwieruch.de/firebase-facebook-login/)
+* [Twitter](https://www.robinwieruch.de/firebase-twitter-login/)
+* [Troubleshoot](https://www.robinwieruch.de/react-firebase-social-login/)
+
+### Activate Verification E-Mail
+
+* add a redirect URL for redirecting a user after an email verification into one of these files
+ * *src/components/Firebase/firebase.js* file
+ * *.env* file
+ * *.env.development* and *.env.production* files
+
+The *.env* or *.env.development* and *.env.production* files could look like the following then (excl. the Firebase configuration).
+
+**Development:**
+
+```
+REACT_APP_CONFIRMATION_EMAIL_REDIRECT=http://localhost:3000
+```
+
+**Production:**
+
+```
+REACT_APP_CONFIRMATION_EMAIL_REDIRECT=https://mydomain.com
+```