Use the Smith Chart display and make sure that the trace is set to S11
And you (very confusingly) need to connect to and calibrate port 0 for S11 measurements. Port 1 (normally 2) is the return port for S21 measurements.
I think that the original nanoVNA designer did a disservice when they labeled the RF ports 0 and 1 (computer style) when everyone else in the known universe's VNA (and the S-parameter numbering and equations) use ports 1 and 2; S11, S21 is a lot more meaningful that way.
Similarly, everyone else uses trace 1,2,3... and save/recall register 1,2,3...
This kind of avoidable confusion has got to be tough on beginners.
Best regards, Don Brant
Donald S Brant Jr