clarify join print-command has to be run on controller

Author: paigecalvert

docs/enterprise/embedded-manage-nodes.mdx

@@ -66,7 +66,7 @@ With Embedded Cluster, you can use the command line to get the commands for join
 
 To automate controller node joins with Embedded Cluster:
 
-1. On a node that is already joined to the cluster, run the following command:
+1. SSH onto a controller node that is already joined to the cluster. On the controller node, run:
 
    ```bash
    sudo ./APP_SLUG join print-command