Now you just have to evaluate $BaseDirectory in Mathematica in order to
now what is your $BaseDirectory, then unzip "modifiedQDENSITY.zip" and copy
the generated "QDENSITY" directory (folder) inside the "Applications" folder
of your $BaseDirectory (or your $UserBaseDirectory), and select "Rebuild
Help Index" from the "Help" menu of Mathematica's Front End. You will have
the QDensity documentation in the "Add-ons" section of Mathematica's Help
Browser, and the QDensity palette in the "Palettes" submenu of the "File"
menu of Mathematica.

written by Jose Luis Gomez,
http://homepage.cem.itesm.mx/lgomez