I can show you right here. Go to the below website and look under the section “How do I get started with FT8 at least”
https://www.digitalshack.org/xiegu-g90-ft8/
It gives an overview of the settings for the radio in that section. Only difference is with the Mode. Set that to U-D instead of USB (USB-Data if I recall correctly)
You will also need the DE19 or CE19 USB-Radio interface. I mostly see G90’s sold paired with this device but if you did not buy yours with the interface you will need to buy one. Also, buy some ferrite cores from Amazon as you may need one to eliminate RF interference on the USB cable.
Screenshots of my WSJT-X settings below:
Obviously use your callsign and gridsquare here!
The COM port may vary depending on which USB port you plug into on your computer.
Under device manager for your computer:
Again, the COM port number may vary but I think the description should be the same.
Audio settings. These devices will only show up when you plug in the USB cable.
WRL - CAT control settings:
Again, COM port number may vary but use the 19200 baud rate.