The G90 is a great radio with good documentation.
If you are new to the G90 and especially if you are new to HF Radio I would recommend downloading the following documents:
CAT control your Xiegu G90 with your PC and start operating in digital modes
Both documents can be downloaded from:
You can also download firmware updates for the G90 from the above sites.
Videos that will help you setup the G90
I highly recommend watching the videos below to learn how to use the G90.