I just took a look at that site and saw the lection "health" with the text:
How to tell doctor about your headache. Wie Sie dem Arzt sagen das Sie Kopfschmerzen haben.
It is the wrong "das" there, you have to use the conjunction, not the article, so the sentence must be:
"Wie Sie dem Arzt sagen
, daß Sie Kopfschmerzen haben."