Hello G. Cerezo,
The SPI for VMware follows the same install as other SPIs (as per HP's Install and Upgrade Guide for the SPI DVD): install the SPI on Node A in a cluster, then install it again on Node B, Node C, and so on, until you've installed the policies and instrumentation to every node in the cluster.
The SPI for VMware has several components - including a collector service, UI, and license/monitoring job server component. The only component we recommend installing on the OMW management server is the one installing the policies and instrumentation, which we call the Management Server Component (the file is VmspiOmwSetup.msi). Please install this component on each node in the cluster.
The other components should be installed to other systems. The nworks management center component (nMC) handles the licensing and provides HA/load balancing among collectors, as Alec mentioned, and it's usually installed on the same system as the UI component. These components can be installed on one of the collector components, or on a separate system (or systems - the nMC and UI don't even need to be on the same system). Our Deployment Guide has additional information on the architecture that you may find useful.