Hi Peter,
Are you on he right page of the manual? This is the one I mean
Select the zero order (with the mouse + left click)
select “spectrometry”, “calibration 1 line”
In the box that pops up:-
enter 0 for “wavelength” (the zero order)
enter the dispersion (A/pixel) that you got from the reference star calibration in “sampling”
Click “apply” and the spectrum of the target star should then be calibrated using the calibration from the reference star
Robin