You cannot just plug two NMEA 2000 devices together with a suitable NMEA 2000 cable – they must be connected to a properly constructed NMEA 2000 network.
Each device has an NMEA 2000 interface that must be powered from the network. Some smaller low power devices, like sensors are also powered from the network
There is a small cost in setting up the network, but future expansion is very easy. A Digital Yacht NMEA 2000 Starter Kit is a cost effective way to build a small, expandable network