As the spectrum is calibrated by respect to itself, it will not be possible to measure doppler effect as it needs to take into account wavelength shift versus the absolute value which you do not have. To calibrate the spectrum of the reference star, you need to identify two lines and to assign through Visual Spec their corresponding wavelength. Once this is done, you have to load the spectrum you want to calibrate. It is mandatory that this spectrum has been recorded in the very same conditions to not introduce errors. The assumption is that the sampling coefficient will be the same for both spectra.
First step is to record the spectrum of a known star for reference, with lines easely identifiable.
Then, this spectrum shall be calibrated. Once done, the sampling coefficient shall be recorded on a piece of paper. If the assembly does not allow to image domain beyond 6600 angstrom, it will not be possible to use atmospheric lines as they will no show up on the spectrum . Now,the spectrum to calibrate is loaded, and it is sufficient to identify only one line. The method is the same as for the reference star.