Hey, thanks for the hint on this one. I was looking to solve the same problem. Your follow up post gave me the clue that I was looking for. To hook up the Spark2/SparkLE to the Drum sequencer on the Beatstep Pro, the MIDI Control Center (for the Beatstep Pro) has a Drum Map option under Device Settings. The drop down menu that you found is called "Drum Map" and it has an option for Spark.
It took me a little time to locate this, so I figured I would put some more details around it while thanking you for the hint.