The Spectroscopy First Steps document, provides step-by-step instructions on how to generate spectra in the RHESSI GUI, produce an output FITS file for input to Richard's SPEX program, and then how to use SPEX to determine the background and obtain least-squares fits to various functional forms. It was originally prepared by David Smith and completed by Brian Dennis with input from Richard Schwartz.
Chris Johns-Krull has prepared an Overview of the Command Line Interface for HESSI Data Analysis Software that describes how to use the IDL command-line interface to generate spectra and provide a data file for input to SPEX.