Hi Rich,
Your laptop connects to one of the Network ports on the MixRack. Alternatively you can set up a wireless access point. See the Director Help for details. The default address for the MixRack is 192.168.1.70, so your laptop will need a compatible, static IP (for example 192.168.1.10) and same subnet (255.255.255.0).
You can update the firmware using a browser. Download the firmware package on your laptop. Type in the MixRack IP address in your browser and you should see a setup page. Select Update Firmware and locate the Firmware.tar.xz archive in the Firmware/TLD-MiRackFirmware folder.
Hope this helps.