The Help center is the application containing all the documentation. The Help Center comes standard with Arbortext Editor (starting with 5.4 F000). You can launch the Help Center directly from inside Arbortext Editor, or separately by going to the Start Menu->PTC->Help Center in Windows.
The tutorial can be found under the "Authoring" section of the Table of Contents.
This tip and many others can be found in Arbortext 101 available in ePub and print on Amazon.
arbortext editor, basics, best practices, training and mentoring