The Domain Controller on the server uses the Microsoft Windows ‘Server Core’ Operating System. This means that you don't connect to it directly via Remote Desktop Services. You perform all of your management and administration tasks from the Windows Management Virtual Machine which exists on each server and is named ZMANAGE. You can find out the IP address of the ZMANAGE virtual machine from the Commissioning Console. (This Virtual machine has an IP address with the last octet being .160.)
Use Remote Desktop Services (RDP) to connect to the ZMANAGE Virtual Machine, and you can then run all the standard Microsoft tools from the Administrative Tools folder. (eg Active Directory Users & Computers)
You can use a local domain admin account, or your Management account to log in to the ZMANAGE virtual machine. If using your Management account, you must use the ZCP domain prefix with your username to logon. Eg ZCP\username.dfg.
You can customize Active Directory however you like, including creating and editing Group Policies, OUs, groups and objects. However, it is strongly recommend that users and groups are kept in the default Organizational Unit for each server which is:
[ Active Directory Domain Name ] > Zynstra > Cluster ID.