NPA-5880: Updated Postman readme

Author: ClarksonAdam

postman/README.md

@@ -1,8 +1,18 @@
-# Postman Collection
+# Postman Collections
 
-This folder contains the Postman collection for the API.
+This folder contains the Sandbox and Integration Postman collections for the VRS API.
 
 > [!WARNING]
 > Documentation and links in this file are specific to the maintainers of this repository and are only available to NHS England staff.
 
-To update the Postman collection follow the steps on the [How to update Postman Collection Confluence page](https://nhsd-confluence.digital.nhs.uk/pages/viewpage.action?pageId=874694621)
+## Updating the collections
+
+To update the Postman collections follow the steps on the [How to update Postman Collection Confluence page](https://nhsd-confluence.digital.nhs.uk/pages/viewpage.action?pageId=874694621)
+
+## Integration collection
+
+The 'integration' postman collection includes requests and examples to be used by the VRS team, consumers, and external
+parties to test against our INT environment.
+
+For details on the environment variables and authorization methods required for this environment, please see the Getting
+Started section within the Postman collection itself.