how to configure enterprise vault Permissions Configurations Exchange Server 1 Forest 2 Domain

My problem can't script permission Configuring the Exchange throttling policy on the Vault Service account.

Permissions Configurations

1. Log on to the Exchange Server in Forest B\Domain B as a user who has the Organization Management role. Run the Enterprise Vault Permissions script against the VSA for this Exchange Server.  (000081287)
   
   Note: The account specified is the VSA in Forest A. The Linked mailbox is not used at this stage. In this example the Exchange Server is called Exch2010, however the same should apply for Exchange 2013.
   
   SetEVExchangePermissions.ps1 –User Domain A\VSA –Server Exch2010 -Action Add –Level ALL –Verbose $true
   
    
2. Log on to the Exchange Server in Forest B as a user who has organization management role and run the Enterprise Vault Throttling script against the Linked Mailbox https://www.veritas.com/docs/000102737 
   
   i.e SetEVThrottlingPolicy.ps1 –User Domain B\VSA_Linked –Server Exch2010 -Version 2010 
    
3. Assign access rights to the System Mailbox configured under the setting section of the task. In this example, this is the EVSysMbx mailbox, which has been checked in step 8 of the 'Validation Steps' section. This step is performed on the Exchange server in Forest B. The User Account to use is the Vault Service account residing in Forest A.
   
   i.e Add-ADPermission -Identity EVSysMbx  -User Domain A\VSA  -AccessRights ExtendedRight -ExtendedRights "send as"