Try the default files by just clicking on the submit button, or type in the path to an XML file and an XSLT file. Note: if I remember right, they must live where this server can get at them directly or they will violate the security model of Ajax. Try just this directory name in your browser to see if other files are present to play with in this directory, or find other files on this (the IT department machine, maserati) to experiment with. Place your own XML and XSL-T files on maserati somewhere, and this script should work with them.
Remember, this is bleeding edge stuff. Some files in this directory work fine, others do nothing at all, and still others spin out of control and hanggggggg. YOYO (you are on your own).
jeffs