AAD Connect : How to add an OU to be synced
Here goes to add an OU for AAD Connect sync.
1. Open AAD Connect Synchronization Service Manager
2. Select on-prem AD connector and click Properties
3. Configure Directory Partitions -> Containers
4. Enter Password and click OK
5. Select an OU to be added, "AAD Connect" in this example
7. A new user, "new_aad" created