Acronis Cyber Protect 15: how to assign Virtual Host license when installing agents inside guest OS of virtual machines

Scenario

You have an Acronis Cyber Protect 15 Standard/Advanced Virtual Host or Universal license or Acronis Cyber Backup 15 Standard/Advanced Virtual Host or Universal license (either subscription or perpetual) and want to back up Citrix XenServer, Red Hat Virtualization (RHV/RHEV), Nutanix AHV, KVM, Oracle virtual machines or virtual machines on a free ESX(i).