SUMMARY

Right now if you open `Kalendar` you got your sidebar with some (existing) calendars.
To add another, delete or manage a calendar (source), you have to dive deep into the buried settings:

1) Settings
2) Configure Kalendar
3) Calendar Sources
(4) Add New Calendar Source)

IMHO this is a feature which should be accessible right from the top screen: 

1) Right click on the sidebar where the calendars are --> Add calendars
2) Right click on a calendar in a sidebar --> Delete / Manage particular calendar

This is how KOrganizer does it, and how you manage your places in Dolphin, etc. and thus I guess very common and probably expected way to work.

I also wonder if the "Calendar" and "Calendar Sources" pages could not be merged: 
Isn't there a 1:1 map between (local/remote) resource and a calendar? Why is it split?