if there is a midi device connected, it’s really easy. I use an M-Audio UNO
(random google result: http://www.bhphotovideo.com/c/used/264002/?gclid=CMeG2cuUrcsCFdGQHwod_WsLPw )
In order to learn more I got a Midi Monitor program, which can “sniff” the midi events and can also act as a midi device itself–> https://www.snoize.com/MIDIMonitor/ This was very helpful detecting if Reaper was sending, and where, or if BeatBuddy was responding etc. Not essential but useful.
Restart Reaper if you’ve plugged in the device after Reaper started.
Click on the ROUTE box.
Click on under MIDI Hardware Output
Select the proper device, M-Audio in this case.
I have both the UNO hardware device (with BeatBuddy attached), and the Midi Monitor program.
Make sure the BeatBuddy midi options make sure it’s listening for midi events, and you should be able to play midi in Reaper, and hear it come out of the BeatBuddy pedal. No more guessing what it will sound like!