All you have to do for running mpshift is typing mpshift at the shell level.
The results of a SCF or DFT calculation (the trace of the total shielding tensors, its anisotropy and the CPHF contribution for each symmetry distinct atom) are written into the control file after the keyword $nmr <rhf/dft> shielding constants.
This data group is write only for mpshift, but you can utilize it for graphical rendering of the calculated NMR spectra and for a quick overview of the results. A more detailed output with the complete shielding tensors can be found in the output of mpshift, so it is recommended to put the output in a file when calling the program.