Slicing / mapping is relatively straight-forward.
(a) browse to your loop and drag it onto a single key in the Keyboard Mapper
>>> http://i.imgur.com/WnKBbC5.png(b) Switch to the Wave Editor, select the loop and slice it (automatically using the Threshold and Transient Slice button at the top) or manually (insert your own slice points)
>>> http://i.imgur.com/WnKBbC5.png(c) If needed (and it generally is), zoom in and nudge the slice points into position, add or remove slice points
>>> http://i.imgur.com/8FpEWcI.png(d) drag the whole loop (not the slices) onto the [Keyboard mapper] button and thence onto a single key in the Keyboard Mapper and lay out the slices.
and 
http://i.imgur.com/KY9Skq4.png and http://i.imgur.com/BPH5sb8.png
(e) (if supported by your DAW,) drag the mapped group of slices into your DAW host (Reaper in this case) to get the MIDI clip to play them in sequence; click Play. Or drag it into File Explorer or your Desktop and load it into your DAW from there.
>>> http://i.imgur.com/mZS3xUA.png