Adding pre-reqs back.

Author: roygara

articles/virtual-machines/disks-enable-host-based-encryption-portal.md

@@ -4,7 +4,7 @@ description: Use encryption at host to enable end-to-end encryption on your Azur
 author: roygara
 ms.service: storage
 ms.topic: how-to
-ms.date: 09/26/2022
+ms.date: 09/27/2022
 ms.author: rogarana
 ms.subservice: disks
 ms.custom: references_regions
@@ -27,6 +27,45 @@ Temporary disks and ephemeral OS disks are encrypted at rest with platform-manag
 
 Legacy VM Sizes are not supported. You can find the list of supported VM sizes by either using the [Azure PowerShell module](windows/disks-enable-host-based-encryption-powershell.md#finding-supported-vm-sizes) or [Azure CLI](linux/disks-enable-host-based-encryption-cli.md#finding-supported-vm-sizes).
 
+## Prerequisites
+
+You must enable the feature for your subscription before you use the EncryptionAtHost property for your VM/VMSS. Use the following steps to enable the feature for your subscription:
+
+1. **Azure portal**: Select the Cloud Shell icon on the [Azure portal](https://portal.azure.com):
+
+    ![Icon to launch the Cloud Shell from the Azure portal](../Cloud-Shell/media/overview/portal-launch-icon.png)
+
+1.	Execute the following command to register the feature for your subscription
+
+    ### [Azure PowerShell](#tab/azure-powershell)
+
+    ```powershell
+     Register-AzProviderFeature -FeatureName "EncryptionAtHost" -ProviderNamespace "Microsoft.Compute" 
+    ```
+
+    ### [Azure CLI](#tab/azure-cli)
+
+    ```azurecli
+    az feature register --name EncryptionAtHost  --namespace Microsoft.Compute 
+    ```
+
+    ---
+
+1.	Confirm that the registration state is **Registered** (takes a few minutes) using the command below before trying out the feature.
+
+    ### [Azure PowerShell](#tab/azure-powershell)
+
+    ```powershell
+     Get-AzProviderFeature -FeatureName "EncryptionAtHost" -ProviderNamespace "Microsoft.Compute"  
+    ```
+
+    ### [Azure CLI](#tab/azure-cli)
+
+    ```azurecli
+    az feature show --name EncryptionAtHost --namespace Microsoft.Compute
+    ```
+    ---
+
 ## Deploy a VM with platform-managed keys
 
 1. Sign in to the [Azure portal](https://aka.ms/diskencryptionupdates).