Login to your iCloud account and click on "Calendar":
Click on the sharing icon next to the calendar you want to add to DAKboard (below, circled in red)
If "Public link" is not checked, check it, then click "Copy link" (also circled in red)
Note: if the sidebar above showing your calendars is not already visible, click on the "Show calendars" link at the bottom:
Now, login to your DAKboard account (https://dakboard.com) and select the screen you would like the calendar to appear on.
If it's a Predefined screen, click the Calendar tab then paste your copied link at the bottom.
If it's a Custom screen, click the "Add a block" button, choose "Calendar", then click the edit button edit the block.
Next, paste the copied link into the iCal URL field:
Optionally give the calendar a name and choose a color.
Click the "Save Changes" button and then view your screen to see the calendar.