Displaying individual spectrum files in IRAF

Please see the Reading individual spectrum files for details on the spSpec FITS file structure. In brief, though: if you want to use splot in IRAF to plot a spectrum, you want to give it a file name like:
spSpec-MJD-plate-fiber.fit[0][*,X]

where X=1 for reduced spectra
      X=2 for spectra with 4th order fit to continuum removed
      X=3 for the error array
      X=4 for the mask array (whatever that is)

Alternatively, you can also just give splot a filename with the [0] extension at the end, then respond with the X from the above list when it asks: Image line/aperture to plot.
Ex.

on> splot
List of images to plot (bob): spSpec-51821-0384-636.fit[0]
Image line/aperture to plot (0:) (0): 1