You will need to install the Cornerstone SDK, or Cornerstone runtime. These are available as an OS X package. The SDK package includes full runtime binaries, so you do not need to install both on the same machine.
The config.txt and screen.xml files are used to connect to the tracker and configure the screen.
config.txt and screen.xml are in /Users/Joe/Library/MultiTouch directory.config-*.txt and screen-*.xml files can be found in