You create a new device, under Devices, and then set this as the Device Type. Your custom Device Types usually show at the end of the list. Then when you first use the Thing on your IOS device, you’ll have to set the values for your Total Comfort login and Thermostat number (assigned by Honeywell, at the end of your URL when logged into Total Comfort website). Alternately, you can set these in the IDE after you create your device and re-look at it, after clicking it in the Devices list of the IDE.
[Also, you apparently set the Device Network ID, when defining the new device to the hex conversion of its IP address. You can find online IP-to-hex converters. I don’t know if this really matters, since the code never seems to talk to the device itself. Instead, it talks to the Honeywell TC website, which in turn talks to your thermostat.]
I should have followed this closer… just finally took the time to debug my devicetype… seems very little changed, they were just a little bit more strict about what cookies they were accepting as well as no longer sending weather data.
To return the favor, I would point you to StatusThing. It puts the status of selected ST things onto your Mac’s status bar. It also allows you to control simple things there as well (on/off things). I find it super useful because when I get home, I put my iPhone on my dresser to be charged and lose my ability to directly control my smart things. I’ve pretty much covered this with a few of the GE remotes (often on sale for around $12) and StatusThing. [Unfortunately, I can’t show the Honeywell Thermostat on StatusThing without crashing, so I just leave it off the list.)
My device type is a blend of the one by @ethomasii and another I found on github. The difference is that I made some tweaks to conform to the new cookie handling by Honeywell and I added some formatting tweaks for the heat and cool setpoints. You can use ST to set the away cool set point and heat setpoint. I don’t know of any way to set the fan mode via a smart app, as I have never done anything like that.