From a previous project I did have a W5500 Ethernet Module (which seems to widely available and relatively cheap), so the challenge was to see if the Xenon could work it.
In the end it turned out to be relatively simple to connect the Xenon to the module through the exposed SPI interface. The back of pcb indicates the pin out details for the W5500. The diagram below details which pins from the Xenon connect needed to be connection W5500 Module.
This post on the Particle site covers how to enable Ethernet and fingers crossed your Xenon should connect to the Particle cloud as mine did.