a level history coursework

What question are you trying to answer regarding the Cold War? Did the teacher give you a topic/question?

My question is:
"Historians have disagreed about the reasons for the end of the Cold War. What is your view about the reasons for the end of the Cold War?"

I'd start with Wikipedia just to read an overview on why the Cold War ended. You may be able to find some sources there to look at in the notes at the bottom of the page:
Cold War (1985–1991) - Wikipedia
With the question you have, I'd suggest examining three to five factors that explain the reason for the end of the Cold War. I'd also suggest you decide which reason you think is the most significant and make sure you explain this in your introduction.
If you go to my profile, you'll find my website. There's a pop up on the website that gives you a free pdf on how to write essays.
Good luck