Mike,
Just set the start and stop frequencies to the widest approximate frequency range where you expect the antenna will be tuned to. For 10M try 25 to 32 MHz. The calibrate for this range. Set the yellow trace to read SWR and you should see a frequency where the SWR is at a minimum. Then use the rocker switch to move the marker to this point and you can read the frequency and SWR. Then slowly adjust your coil and you should see the SWR minimum move. You can "zoom in" by setting the start a bit higher and the stop a bit lower and the NanoVNA will interpolate the calibration.
Roger
Roger Need