I just want to start with the fact that I do not use session drummer, so I am no expert.
What are you seeing on the left hand side of the piano roll view? Piano keys or drum names? As far as I can tell from a brief look just now, if you insert Session Drummer as a Simple Instrument, or as a MIDI source and Audio Out, or if you route the output of a MIDI track to Session Drummer, it automatically loads the Session Drummer Drum Map.
If the names are no use to you e.g. if the sound assigned to the snare is a wolf howl and the bass drum is a cement mixer, then you could try creating a new drum map based on the session drummer preset.
On the MIDI track select Drum Map Manager from the output button, create a new map, load the session drummer preset and simply type the new names in place of the old.
I hope that makes sense.. As I said, I don't use session drummer, but I'm sure someone with more experience will chime in if I am mistaken.