V4.1 is the latest release for the Facet, so you are up to date.
As far as updating, I prefer a SerialUSB connection with an Android tablet.
You will need a Serial Terminal on your Android, and there is a niffy connection guide from Sparkfun.
For the Firmware Uploader GUI on your Windows machine, go here
And Download the zip file highlighted below for Windows
The compiled binaries (to use with the Firmware Uploader GUI) are here:
If you weren’t already on V4.1, you would download it
Click the .Bin file you want, then in the Top Right corner of the next page you should see :
