At this stage both the packages built for Cronos II have support for the new address book compiled in. (i.e. the RPM available from the web site and the Debian package available via unstable packages (apt-get install cronosII)
The address book is a relatively new feature for Cronos. As of CronosII version 0.2.2 it works very well however much more is planned for this particular extension to Cronos and so it must still be considered to be an early form of what promises to be a very powerful stand alone application in its own right.
FIX ME: Complete this
The address book is an application in its own right
You will find it on your gnome menus as a separate (2nd) Address book
When you save the contents of your address book you will find them auto-magically in your Gnome Card default book and Visa Versa (I just checked !)
You do need to save when you have finished making entries
As you enter addresses into the fields you should find that they either auto complete or you are presented with a list of choices from your book.