Hi
You need two servers (physicial) or two VMs or even one VM and one server. So you need just minimum two CPPS doesn't matter are they VMs or physicial.
Then you have to configure one of CPPMs to be subscriber. Let's say as subscriber is slave unit.
Subscriber will synchroznie to Publisher unit. For details refer to CPPM documentation - setup is very simple. Just be sure that both CPPMs are in same version and same patchlevel.
If you want active/passive redundancy then you can configure Virtual IP for both servers. Another solution is just to define two Radius/Tacacs server in your network devices configuration.
Rob