So you have a network relay board and you want to control it with Indigo. Hopefully this post will give you enough information to get going.
The relay board does not come with DHCP enabled. It has a static IP of 192.168.1.166 in the subnet 192.168.1.0/24 (subnet mask 255.255.255.0). If your network is in this same subnet then you should be able to plug the device in and get going right away. If your network is in a different subnet, then you will need to set a static IP on your computer in the same subnet and connect the device directly without your network. You can access the web interface, configure the device, and set a static IP in your network's subnet. If you need help with this process, please open a forum topic and we'll try to guide you through setting an IP on the relay board.
Once you know your device's IP you can go ahead and add it to Indigo. Select New Device, then 8 Channel Network Relay Board. On the screen that comes up, put in the IP if it's different than the default. Now click the Add Relay button. You can add up to 8 relay or 8 input sensors, or a combination up to 8 total devices. Since the relay board has 16 total devices (8 relays and 8 inputs) you will have to create at least 2 separate 8 Channel Network Relay Board devices to access everything. The plugin is smart enough to recognize a duplicate IP and only poll the device once even if it exists multiple times. It is perfectly fine to add a separate device per relay instead of adding 8 in one device; everything pretty much works the same way in this alternate configuration.
After adding some relays and/or inputs, click Save. If you click Cancel, your changes will be lost. Now edit each device's settings and select a relay channel. The channel corresponds to the relay number on the board. With the ethernet port facing down, channel (relay) 1 is on the left, channel 8 is on the right. That's it. Click Save and try to control your relays. They should click when you turn them on or off.
If things are not working, check the Indigo logs for clues.