I think if you go to:
Config Your Desktop > Workspace Appearance and Behavior > Akonadi Configuration
and choose Add and scroll down to KDE Calendar (Traditional)
Press Next at the first prompt and then choose Calendar in Local Directory
It will then ask for a folder location which would be
The next option is for naming the calendar which can be anything you like.
If you then open Korganizer you should see your calendar - tick the box next to it for it to become "active"
If you already have a backed up calendar, or another one you'd like to use, open Korganizer and use File > Import > Import Calendar and choose calendar location.
KDE have a Release Schedule Calendar which can be downloaded and used