If you install View Composer on a different machine than vCenter Server, you must create a domain user account in Active Directory that Horizon 7 can use to authenticate to the View Composer service on the standalone machine.
The user account must be in the same domain as your Connection Server host or in a trusted domain. You must add the user account to the local Administrators group on the standalone View Composer machine.
You specify this user account when you configure View Composer settings in Horizon Administrator and select Standalone View Composer Server. See Configure View Composer Settings.