When you configure VMware Horizon for the first time and want to use instant clones, you will need to provide an instant-clone user, called the instant-clone domain administrator in Horizon Console.
The instant-clone domain administrator is a user account in Active Directory that allows Connection Server to perform certain operations related to instant clones in Active Directory. Connection Server requires this account to join instant-clone virtual machines to your Active Directory domain. See Create a User Account for Instant-Clone Operations.
After you create and configure this instant-clone domain administrator account, you can specify the user name in Horizon Console.