I've installed Studio Drummer and Reaper. I've done the basic setup in Reaper for the VST plugin and can pull the pre-recorded tracks from Studio Drummer into Reaper and it appears in the track as a MIDI file. How do I get this MIDI track to playback with the VST sounds?
You need the VST loaded in the track's FX list. MIDI data in REAPER tracks passes through the FX, and there needs to be some plugin there to interpret the MIDI and produce sounds, which are then passed to the track's output. This is true for any VST instruments in REAPER, not just Studio Drummer.
Don't forget to check that the track monitoring is set correctly as well!