It's not a tutorial, but the BoardSim User Guide has the best information. Look at Chapter 24 - Simulating EMC with the Spectrum Analyzer. The documentation is available from within BoardSim under the Help menu.
Running the simulation is quite easy, but understanding the algorithms and effects is not so easy. The simulation is basically, verify correct stackup, verify specification of power nets, assign IC models (IBIS), run the Spectrum Analyzer.
Let us know if you have some specific questions about the procedure.
I will try following your suggests and in case off, I'll back to you.