Like in the telnet post, you can have Netsight running as a VM in VirtualBox for training purposes. It will manage your VMs. Again, just make sure to have all adapter 1 of all VM in the VB Host-only network, set your Netsight in that same network, and they will all see each other.
NetSight is using mainly SNMP for managing switches. you need to configure NetSight to use the same SNMP credentials as your switch is configured. It depends on your XOS config. in general default XOS does have SNMPv2 "public" for reading and "private" for read/write. configure the NetSight to use the same, establish IP/UDP connectivity between your switch and NetSight and you are good :)
Actual version of NetSight (Extreme Management Center) does have pre-configured SNMP profiles for XOS out-of-the-box.