For servers - you’d need to install netxms agent and set
MasterServers = IP-address-of-your-netxms-server
in nxagentd.conf
After adding a node in netxms, it should detect that agent is present on that system, then you can add DCIs (data collection items) for the metrics that you need.
Also, check the docs, there’s some info there:
https://www.netxms.org/documentation/adminguide/concepts.html
https://www.netxms.org/documentation/adminguide/quickstart.html