How to add US Holidays to KOrganizer Calendar?

Hi all,

I'm trying to find out how to make the US Holidays appear in KOrganizer 
Calendar. Here's what I have been doing:

Right-click the taskbar clock > Configure Digital Clock > Calendar
- checkmark on "PIM Events Plugin"
- checkmark on Holidays

Still in the Digital Clock Settings, in click on Holidays on the left and put 
a checkmark on us_"en-us United State Holidays"

The Holidays show on the calendar that appears by clicking the taskbar clock, 
but they don't show in KOrganizer Calendar.

I didn't see anywhere in KOrganizer to add the US Holidays.

Am I missing something?

Thanks,
JJ