Two methods. It depends if you want to edit the MIDI in Reaper or keep using the song builder/layout in EZDrummer.
If you want to keep editing in EZDrummer, then right click the track and render it. This will create an audio track of the drums.
If you want to edit MIDI in Reaper, then select all the midi in the song builder and drag and drop it onto the track in Reaper. If you do this, make sure you remove all the blocks from the song builder, otherwise it will play both.
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