Extract the downloaded file (xyzrgb_dragon.ply.gz) using 7Zip or others
Start MeshLab : http://meshlab.sourceforge.net/ *We need to use MeshLab for conversion, because the file format is Binary PLY (not yet supported in unity converter)
Meshlab, File/Import Mesh..
Browse to your extracted file "xyzrgb_dragon.ply" and import it
You should now see the dragon inside MeshLab
Meshlab, File/Export Mesh as..
Select export format from "Files of type" dropdown: "XYZ Point Cloud (with or without normals) (*.xyz)"
Click save, export settings dialog appears
Disable [ ] Normals (not needed now)
Copy the exported file "xyzrgb_dragon.xyz" into your unity project Assets/ folder
Close MeshLab
Importing to Unity
Start Unity
Window / PointCloudTools / Convert Point Cloud To Binary
Drag & Drop "xyzrgb_dragon.xyz" file into the Point Cloud source file - field
Select Input File Format: XYZ
Enable [x] Scale values: 0.1
Disable [ ] Flip Y & Z values
Enable [x] Auto-offset near 0,0,0
Disable [ ] Add manual offset
Click "Convert" button
Set output filename and folder (for example "dragon.bin" at Assets/ root folder)
Open "BinaryViewerDX11.scene" from PointCloudTools/PointCloudBinaryViewerDX11/Scenes
Select "@BinaryViewer" gameobject from Hierarchy
Set Base folder to: "" (leave the field empty)
Set file name to: "dragon.bin"
For Cloud Material field, select material: "PointCloudSingleColorDX11"
Hit Play and you should see dragon point cloud in unity