USB tethering phones in 4.2.0rc5

Is there anywhere guide for this, please? I tried on my own using common sense and what I already knew about Qubes (far from enough, of course and obviously), but eventually didn’t succeed. At the end, my sys-usb took the role of sys-net. I did it without problems with other kind of external USB network devices, though. For example, this.

Step by step guide would be immensely appreciated.