What are you trying to achieve, connecting to a network to access through a PC or have another device (PLC, DCS, SCADA) communicate with the Omni? You need to configure the Ethernet port in the Omni and give it a IP address and a modbus id. This can be done either through the front panel in program mode or connected to a PC with Omnicom software. You can download the Omnicom software free from Omni's website. If you give me a few more details I may be able to help.
Best,
Kenny