Login to your iCloud account

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)

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.