Right now routers supporting UPnP or NAT-PMP are configured automatically to pass connections to NoMachine and all required information is displayed at initial screen (Welcome to NoMachine).
Routers not supporting UPnP or NAT-PMP and Firewalls have to be configured manually to pass traffic to port 4000 (NX protocol), 22 (SSH protocol on Linux/MacOSX) or (4022) (SSH protocol on Windows).
Additionally, your NAT service is running on Virtual Box which means that it cannot be configured automatically with help of UPnP or NAT-PMP. To do it manually please refer to: https://www.virtualbox.org/manual/ch06.html#natforward