To use DITA2Go effectively to produce DocBook output, you need a basic knowledge of DocBook, from study of other materials. Teaching our customers DocBook is beyond the scope of the DITA2Go User's Guide. You have to know what you want; then perhaps we can tell you how to make it happen with DITA2Go.
If you are not familiar with DocBook, here is a good starting point:
http://www.docbook.org/tdg/en/html/docbook.html
If you intend to produce output from the DocBook XML files DITA2Go produces, you will also need DocBook XSL: The Complete Guide by Bob Stayton: