Instructions from "​https://lidarbb.cr.usgs.gov/lofiversion/index.php?t1248.html"

1) Select the shapefile in ArcMap or ArcCatalog
2) Right mouse click and export-> to CAD
3) I usually change it to DGN_V8, but that is because I have Microstation V8
4) Change the seed file to seed3dcm.dgn (not sure if this is required, but I do it)
5) Your shapefile will now be a dgn you can open in Microstation

In Microstation, you would then select the polygon(s), open a new project in Terrascan, and select add by boundaries. You would get empty project files for each polygon, and then you could then Import points into project that would be binned out by each polygon you had.