At the most basic level, you'll need to create a new track, load up Superior Drummer as an effect in the FX window, and then create a new MIDI item. Then just put MIDI notes on the piano roll and make your beats.
For using effects and VSTi's
http://www.cockos.com/wiki/index.php...2FVSTi_Effects
For using the MIDI editor
http://www.cockos.com/wiki/index.php/MIDI_Editor
Sorry for the short response. Can you tell us where you are running into trouble?