prereq section fixes

Author: brhamilton529

articles/spring-apps/how-to-enterprise-large-cpu-memory-applications.md

@@ -23,8 +23,9 @@ This article shows how to deploy large CPU and memory applications in Azure Spri
 
 ## Prerequisites
 
-- An Azure Spring Apps service instance.
-- [The Azure CLI](/cli/azure/install-azure-cli).
+- An Azure subscription. If you don't have a subscription, create a [free account](https://azure.microsoft.com/free/) before you begin.
+- An Azure Spring Apps service instance. For more information, see [Quickstart: Provision an Azure Spring Apps service instance](/azure/spring-apps/quickstart-provision-service-instance).
+- The [Azure CLI](/cli/azure/install-azure-cli). Install the Azure Spring Apps extension with the following command: `az extension add --name spring`.
 
 ## Create a large CPU and memory application