Update README.md

add instructions for setting prefix

README.md

@@ -3,7 +3,15 @@ angular-local-storage
 
 An Angular module that gives you access to the browsers local storage
 
-Remember to set your app name (settings.appPrefix) in the settings at the beginning of angular-local-storage.js.
+Remember to set your app name (settings.appPrefix) in the settings at the beginning of angular-local-storage.js:
+
+```javascript
+angular.module('LocalStorageModule').value('prefix', 'myPre');
+angular.module('testApp', ['LocalStorageModule'])
+  .config(function ($routeProvider) {
+    ....
+});
+```
 
 To do:
 - Add tests