You have a couple of options to hear it in REAPER:
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use the internal drum samples (virtual instruments) of your computer, see this post for additional information, Reaper output volume problem
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connect BB Pedal to your computer using MIDI cables. You will need the BB Sync adapter cable, MIDI cable and Audio/MIDI interface device (this is usually your external sound card with MIDI input/output if you have one). Then, configure REAPER to use the MIDI Out of the sound card.