Open up IRAF
Load the NOAO package
Load the onedspec package
eparam sbands
have a list of neccesary files ready before you begin.

First you need to "calibrate" (for want of a better term) sbands.
We use a spectra from Vega for this reason.  Convention states that at every
wavelength, Vega's magnitude is zero.  So first, you have to run sbands on a
spectrum of Vega to provide IRAF with a zero point.  Make sure you write down
all calculations before entering the appropriate values!  Don't spend 4 hours
trying to figure out what you did wrong.

Having eparam'ed sbands, you should see the following:

PACKAGE = onedspec
   TASK = sbands

input   =            		Input list of spectra 
output  =               	Output file name
bands   =                	Bandpass file
(apertur=                     ) Apertures
(normali=                  yes) Normalize the bandpass response?
(mag    =                  yes) Output results in magnitudes?
(magzero=                   0.) Magnitude zero point
(verbose=                  yes) Verbose header?
(mode   =                   ql)

Mike should've given you the appropriate Vega spectra, and the bandpass file.
You need to create a bandpass info file which tells IRAF just what the bandpass
is like.  This is any text file with the following format (one space between
each field)

"Identification string" "central wavelength" "bandpath width" "filter filename"

If I were to do an H-band sbands operation, my info file would look like this:

H 16320 2380 H_184.txt

I'd save it to a file named "hband" (makes it easy to remember).

So now, on to the actual work of it.

You are given a file that has the values for Vega's spectrum.  Chances are its 
a text or data file, which may or may not be a problem, depending on your level
of IRAF fluency.  Essentially, you need to convert that file into a fits image.
If you don't know how to do that, ask Mike, Justin, or me when you get the
opportunity.

So let's review what files we have so far (all in your IRAF directory):
vega.dat	not necessary, but if you go and mutilate the fits image, you 
		can always make a new image
vega.fits	necessary for your success
hband		ditto
H_184.txt	the filter file, which should've been provided to you.  This
		one is neccessary, even if we never directly manipulate it in
		IRAF

If you're missing any of these, check your notes.

eparam sbands has been sitting there for a while hasn't it?  Now we can do
something with it.

Make your screen look like this (changing the file names to fit your naming
conventions and situation)

PACKAGE = onedspec
   TASK = sbands

input   =           vega.fits	Input list of spectra 
output  =           STDOUT    	Output file name
bands   =           hband     	Bandpass file
(apertur=                     ) Apertures
(normali=                  yes) Normalize the bandpass response?
(mag    =                  yes) Output results in magnitudes?
(magzero=                   0.) Magnitude zero point
(verbose=                  yes) Verbose header?
(mode   =                   ql)

move your cursor down to the "mode" field, type :go and press enter.  Assuming
all went well, you should get an output like this:

# SBANDS: NOAO/IRAF V2.11EXPORT petsfed@zulu.uwyo.edu Fri 10:39:56 26-Sep-2003
#   bands = hband, norm = yes, mag = yes, magzero = 0.00
#       band     filter wavelength      width
#          H  H_184.txt     16320.      2380.
#
#                 spectrum    band         mag
              vega.fits(1)       H     24.8702

Note the number under "mag".   now eparam sbands again.

PACKAGE = onedspec
   TASK = sbands

input   =           vega.fits	Input list of spectra 
output  =           STDOUT    	Output file name
bands   =           hband     	Bandpass file
(apertur=                     ) Apertures
(normali=                  yes) Normalize the bandpass response?
(mag    =                  yes) Output results in magnitudes?
(magzero=	      -24.8702) Magnitude zero point
(verbose=                  yes) Verbose header?
(mode   =                   ql)

See how I changed the "magzero" value to the opposite of the "mag" that it
spit out originally?

If I tell it to run sbands again, it will then tell me that the magnitude for
that band is now 0, which is what we want.

Now, when you run sbands on some other spectra, so long as the only thing you
change is the input spectrum, then IRAF will always output the actual magnitude
for that particular band.  Neat huh?