Identify where to install SCOM Agent on SCCM Site hierarchy.

Hello..
We have a SCCM Site environment where there is one CAS site, other 5 Primary site servers and one DB server .All are in different machines (7 VMs).i need to monitor complete SCCM site hierarchy.Next on which machines i need to install SCOM Agent on both CAS and all Primary Site Server.

Thanks
RICHA KM