Load up some drums on your redrum. Look down at your sequencer track at the bottom and make sure the midi symbol appears on your redrum track - if it doesn't, click on the far left of the sequencer track and then it will appear. The lowest keys on your keyboard should now trigger the drum sounds.
If you can't get your keyboard to control anything in Reason you may have the midi set up wrong. Go "edit" then "preferences" then "midi". Make sure the soundcard is right and then check through the midi receive channels. You might be able to set your keyboard to transmit on a specific midi channel. Make it transmit on 1 and then make Reason receive on 1.
If you still have problems then make sure your leads are plugged in correctly. The midi out from the PC into the midi in of the keyboard, the midi out of the keyboard into the midi in of the pc.
Failing that I don't know.
