How can I ask "what does 하다 mean in English?" and "how do I use ~ㄴ/ 는지 in a sentence?"
I'm just using 하다 as an example. But I would definitely like to know how to ask "how do I use ~ㄴ/ 는지 in a sentence?". I keep hearing it, and I don't know exactly how to use it within a sentence.
Cheers,
Matthew

Question

How can I ask "what does 하다 mean in English?" and "how do I use ~ㄴ/ 는지 in a sentence?"
I'm just using 하다 as an example. But I would definitely like to know how to ask  "how do I use ~ㄴ/ 는지 in a sentence?". I keep hearing it, and I don't know exactly how to use it within a sentence. 
Cheers,
Matthew

Answer

and  "ㄴ/는지" is abbreviation of "ㄴ/는지 아닌지"
it means "don't know exactly noun/verb/adjective or not"

ex) 나는 그 남자가 독일인인지 미국인지 모른다(모르겠다)
      = I don't know exactly he is a German or American

그녀는 내가 중국인인지 한국인인지 안다
       = She know exactly I am Chinese or Korean

그 남자는 그 집이 더러운지 모른다
      = He don't know exactly that house is dirty

나는 이 음식이 맛있는 음식인지  안다
      = I know exactly this food is yummy

I hope my anwer would help you

Answer

하다 means do in English

공부하다 = studying
공부를 하다 = doing study

Answer

It is a 'connective ending' which associates a vague questions with fact or decision of the next clause.
For example, as you said, "I don't know exactly how to use it within a sentence." can be translated as "그것을 문장 안에서 어떻게 사용하는지 나는 정확히 모르겠다."
→ how to use it within a sentence (a vague question) + I don't know exactly (decision)
I hope these answers your question.