ePO can manage a system joined to the same domain as the ePO server, a system joined to a different domain, or a non domain joined system. All that ePO requires is the ability to communicate with the Agent.
This article describes how to move clients from one ePO server to the other. You can also use the Deploy Agent feature to deploy an Agent for your main ePO server over the existing Agents on clients managed by the other servers.
When you configure the one server, you may want to take into consider many factors, including the size of your network and the hardware you use. See pages 17 - 28 - Configuring your hardware to match your network and node count.
Best Practices Guide Revision B McAfee ePolicy Orchestrator 5.1.0 Software