Based on your comment about searching for a brand, I’m going to guess you’re using the new app rather than the classic. To pair zigbee or z-wave devices that aren’t officially supported using the new app you need to put the device in pairing mode and then use the “Scan” option in the upper right of the add device menu. That said, while you may be able to pair the fan controller with the new app, the device handler that this thread is about has extremely limited functionality with the app, and you’re much better off using the classic app instead.
Unfortunately if you’ve not added custom device type handler before, a “simple” walk through for installing this device and the custom code required to get it to work doesn’t really exist. It’s just not a simple procedure. I would suggest you read this FAQ first, which will explain the basics of adding custom code in SmartThings, and then come back and read this thread starting at the very beginning.