This app is very east to use, just set the comm port and click the connect button. Then set your frequency range and display type you want. You then go through the calibration procedure using the short,open,and load standards provided. You can also calibrate for through, and isolated if you are going to do something like checking filter responses.
My multi-band antenna is a G7FEK which gives me coverage on 80,40,20,and 15 without a tuner. I figured this would be a good test of the VNA. I did the scan with a display set to Smith chart. You can see that the impedance is near 50 ohms across the sweep.
You can move the cursor across the sweep and see frequency, impedance, resistance and reactance at that point on the chart.
By using the drop-down you can change the display to Return Loss
One thing I really like about this software is the ability to scale the data to the range you like, or have it auto scale for you.
Now I just need to play with it some more and try checking filters, and see what else it can do. Have also been following activity on the nanovna-users on groups.io and see that additional app are already being developed for it.