add doc for vmss automatic instance repairs

Author: avirishuv

articles/virtual-machine-scale-sets/virtual-machine-scale-sets-automatic-instance-repairs.md

@@ -22,31 +22,69 @@ Enabling automatic instance repairs for Azure virtual machine scale sets helps a
 
 ## Requirements for using automatic instance repairs
 
-**Opt-in to the preview for automatic instance repairs**
+**Opt-in for the automatic instance repairs preview**
 
-Use either of the following ways to opt-in to the preview for automatic instance repairs. These steps will prepare your subscription for enabling the preview feature. 
+Use either the REST API or Azure PowerShell to opt-in for the automatic instance repairs preview. These steps will register your subscription for the preview feature. Note this is only a one-time set up required for using this feature. If your subscription is already registered for automatic instance repairs preview, then you do not need to register again. 
 
 REST API [Features - Register](/rest/api/resources/features/register) 
 
 ```
 POST on '/subscriptions/{subscriptionId}/providers/Microsoft.Features/providers/Microsoft.Compute/features/RepairVMScaleSetInstancesPreview/register?api-version=2015-12-01'
 ```
 
-Azure PowerShell cmdlet [Register-AzureRmProviderFeature](/powershell/module/azurerm.resources/register-azurermproviderfeature)
+```json
+{
+  "properties": {
+    "state": "Registering"
+  },
+  "id": "/subscriptions/{subscriptionId}/providers/Microsoft.Features/providers/Microsoft.Compute/features/RepairVMScaleSetInstancesPreview",
+  "type": "Microsoft.Features/providers/features",
+  "name": "Microsoft.Compute/RepairVMScaleSetInstancesPreview"
+}
+```
+
+Wait for a few minutes for the *State* to change to *Registered*. You can use the following API to confirm this.
+
+```
+GET on '/subscriptions/{subscriptionId}/providers/Microsoft.Features/providers/Microsoft.Compute/features/RepairVMScaleSetInstancesPreview?api-version=2015-12-01'
+```
+
+```json
+{
+  "properties": {
+    "state": "Registered"
+  },
+  "id": "/subscriptions/{subscriptionId}/providers/Microsoft.Features/providers/Microsoft.Compute/features/RepairVMScaleSetInstancesPreview",
+  "type": "Microsoft.Features/providers/features",
+  "name": "Microsoft.Compute/RepairVMScaleSetInstancesPreview"
+}
+```
+
+Azure PowerShell cmdlet [Register-AzureRmResourceProvider](/powershell/module/azurerm.resources/register-azurermresourceprovider) followed by [Register-AzureRmProviderFeature](/powershell/module/azurerm.resources/register-azurermproviderfeature)
 
 ```azurepowershell-interactive
+Register-AzureRmResourceProvider `
+ -ProviderNamespace Microsoft.Compute
+
 Register-AzureRmProviderFeature `
  -ProviderNamespace Microsoft.Compute `
  -FeatureName RepairVMScaleSetInstancesPreview
 ```
 
-Wait for a few minutes to ensure that the *RegistrationState* changes to *Registered* and then run the following cmdlet.
+Wait for a few minutes for the *RegistrationState* to change to *Registered*. You can use the following cmdlet to confirm this.
 
 ```azurepowershell-interactive
-Register-AzureRmResourceProvider `
- -ProviderNamespace Microsoft.Compute
+Get-AzureRmProviderFeature `
+ -ProviderNamespace Microsoft.Compute `
+ -FeatureName RepairVMScaleSetInstancesPreview
  ```
 
+ The response should be as follows.
+
+| FeatureName                           | ProviderName            | RegistrationState       |
+|---------------------------------------|-------------------------|-------------------------|
+| RepairVMScaleSetInstancesPreview      | Microsoft.Compute       | Registered              |
+
 **Enable application health monitoring for scale set**
 
 The scale set should have application health monitoring for instances enabled. This can be done using either [Application Health extension](./virtual-machine-scale-sets-health-extension.md) or [Load balancer health probes](../load-balancer/load-balancer-custom-probe-overview.md). Only one of these can be enabled at a time. The application health extension or the load balancer probes ping the application endpoint configured on virtual machine instances to determine the application health status. This health status is used by the scale set orchestrator to monitor instance health and perform repairs when required.