Uh for solo Redrum mapping (means you select Redrum in the input box to the left) its quite easy...just go into Remote Override Edit Mode and map the pads to your liking.

The tricky part is when you wanna use a Subtractor synth and Redrum at the same time...it can be done, just need to config Bus 10 as "Redrum In" and you can use 1 hand to play a synth part and the other hand to press the trigger pads for drums

BUT

When you press a trigger pad in this config, it also triggers the lowest notes on the kb (low C until low A) for the Subtractor synth sometimes sounds nice (gritty drum sound, especially with sawtooth waves) sometimes doesn't.
But I think drum notes are just better handled with a electronic drumset (for MIDI freaks only)