docs: add note in installer reference

docs/docs-content/clusters/edge/edge-configuration/installer-reference.md

@@ -42,6 +42,11 @@ listed in alphabetical order.
 You can point the Edge Installer to a non-default registry to load content from another source. Use the
 `registryCredentials` parameter object to specify the registry configurations.
 
+If you are using an external registry and want to use content bundles when deploying your Edge cluster, you must also
+enable the local Harbor registry. For more information, refer to
+[Build Content Bundles](../../edgeforge-workflow/palette-canvos/build-content-bundle.md) and
+[Enable Local Harbor Registry](../../site-deployment/deploy-custom-registries/local-registry.md).
+
 | Parameter                                    | Description                                                                                                                                                                                                                                                                                                   | Default |
 | -------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------- |
 | `stylus.registryCredentials.domain`          | The domain of the registry. You can use an IP address plus the port or a domain name.                                                                                                                                                                                                                         |         |