I'm guessing all you need is the 'source file' in the add news source tab?
If so, simply go to the BBC news section you want to incorporate into the ticker, scroll down to the red bar at the bottom of the page, and copy the link that says 'RSS version'. If you paste this into the 'source file' parameter in KNewsticker, this should work nicely.
For example, the source file for the front page news is:
Hope this helps.