Link to the website: http://www.vms4dj.com/
Step-by-step instructions for the recommended setup can be found in the Mixxx user's guide for the VMS4.
C:\Program Files\Mixxx\midi (technically %PROGRAMFILES%\Mixxx\midi)/Applications/Mixxx.app/Contents/Resources/midi/usr[/local]/share/mixxx/midiThe latest official MIDI mapping and script file are in the 1.10 release branch and can be downloaded from here:
The latest official MIDI mapping and script file are in the 1.9 release branch and can be downloaded from here: