added note about where to find authentication credentials

Author: tschie

src/main/java/com/esri/samples/map/create_and_save_map/README.md

@@ -16,13 +16,26 @@ on your portal. Click the Save button to save the map to the chosen folder.
 <ol>
   <li>Create an <ccde>ArcGISMap</code> with a <code>Basemap</code> and operational layers</li>
   <li>Create an <code>OAuthConfiguration</code> with your portal and app credential.</li>
-  <li>Add the configuration to the <code>AuthenticationMangager</li>
-  <li>Create a <code>Portal</code> and load it. Use a custom <code>AuthenticationChallengeHandler</li> to 
+  <li>Add the configuration to the <code>AuthenticationMangager</code></li>
+  <li>Create a <code>Portal</code> and load it. Use a custom <code>AuthenticationChallengeHandler</code> to 
   authenticate with your username and password</li>
   <li>Once authenticated, save the map by calling <code>map.saveMapAsAsync()</code>, passing in the title, tags, 
   description, and portal folder</li>
 </ol>
 
+<h2>Authentication</h2>
+This sample uses the <a href="https://developers.arcgis.com/authentication/#named-user-login">named user login</a> 
+authentication pattern.  As a developer, you will need the following to make use of this pattern:  
+
+<h3>Your apps <b>Client ID</b></h3>
+Login to your <a href="http://developers.arcgis.com">ArcGIS Developers site</a> account and <a href="https://developers.arcgis.com/applications/#/new/">Register</a>
+ your app. Once registered, select the <b>Authentication</b> tab taking note of your <b>Client ID</b>.
+
+<h3>A custom <b>Redirect URI</b></h3>
+
+While still under the <b>Authentication</b> tab in your account, navigate down the page to the <b>Redirect URIs</b> 
+section to setup the redirect URI. 
+
 <h2>Features</h2>
 
 <ul>