We don't know how Desktop Central works exactly, but there is a couple of ways to automate NetGenius installation:
It can be made a part of a machine image deployed to target machines.
It can be launched at the target machine with /SILENT or /VERYSILENT command line parameters. It's also possible to specify components to install. For example, this command will install only the service, without GUI:
netgenius_setup.exe /COMPONENTS="svc" /SILENT
In both cases it's possible to deploy a configuration file and licence as well, so everything will work without additional configuration.