PC phone jack goes to uBitx Mic jack.
PC mic jack goes to uBitx phone jack..
Connect a USB cable.
Assuming you want to run FT8, in the WSJTX software, configure the rig as Yaesu FT-817. Select the COM port for the uBitx, baud 38400. PTT method: CAT, everything else at default.
Depending on your PC, you may have to go to the audio tab in WSJTX and select the input and output devices. The only other thing you need to be concerned with is the volume settings to get the levels right. I find that on my uBitx V5 I need to turn the volume pot almost all the way down to stop it from clipping in the software.
Good luck and 73,