Added link to additional security verification page

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cc: @curtand

Author: MarileeTurscak-MSFT

articles/active-directory/user-help/multi-factor-authentication-setup-auth-app.md

@@ -25,7 +25,7 @@ You can set up an authenticator app to send a notification to your mobile device
 
 ## Set up the Microsoft Authenticator app to send notifications
 
-1. On the **Additional security verification** page, select **Mobile app** from the **Step 1: How should we contact you** area.
+1. On the [Additional security verification page](https://account.activedirectory.windowsazure.com/proofup.aspx?proofup=1), select **Mobile app** from the **Step 1: How should we contact you** area.
 
 2. Select **Receive notifications for verification** from the **How do you want to use the mobile app** area, and then select **Set up**.