It's mandatory for beginners to start reading the documentation (RTFM).
OCS server only inventories computers using the installed agent.
And there is NO agents for others kinds of materials.
BUT, OCS can also discover others hardwares as routeurs, firewalls, switch (with @ip), printers, host like VMware, Ip phone, ... any hardware with a IP stack.
The discovery use ping or snmp scan : maybe you can retrieve more information with hardware with snmp agent included like printers, firewall, routeurs, ... : don't expect a 'full inventory' with snmp, it's a new functionnality