Translation:The house is dark.
(house or home sentence:)
집에 어두워요 is how I see writing "It is dark at home" or "At home, it is dark."
Our lesson sentence 집이 어두워요 is "The house is dark". Or if i was talking about my home, I might translate to "My home is dark." because we do not always need the 져의 for "my" when we both understand we are talking about my home or house.