Update AZ400_M06_L15_Azure_Deployments_Using_Resource_Manager_Templates.md

Author: yashints

Instructions/Labs/AZ400_M06_L15_Azure_Deployments_Using_Resource_Manager_Templates.md

@@ -225,6 +225,16 @@ In this task, you will modify the main template to reference the template module
 1. In the Cloud Shell pane, click the **Upload/download files** icon and, in the dropdown menu, click **Upload**.
 1. In the **Open** dialog box, navigate to and select **C:\\templates\\main.bicep** and click **Open**.
 1. Follow the same steps to upload the **C:\\templates\\storage.bicep** file too.
+1. From a **Bash** session in the Cloud Shell pane, run the following to perform a deployment by using a newly uploaded template:
+
+   ```bash
+   az deployment group what-if --name az400m13l01deployment --resource-group az400m13l01-RG --template-file main.bicep
+   ```
+
+1. When prompted to provide the value for 'adminUsername', type **Student** and press the **Enter** key.
+1. When prompted to provide the value for 'adminPassword', type **Pa55w.rd1234** and press the **Enter** key. (Password typing will not be shown)
+1. Review the result of this command which validates your deployment and let's you know if there is any errors in your templates. This is very valuable especially when deploying templates with many resources and in business critical cloud environments.
+
 1. From a **Bash** session in the Cloud Shell pane, run the following to perform a deployment by using a newly uploaded template:
 
    ```bash