Q: Need help! Required before Monday 8 March 2016

I don't know that I have an answer for you, not least because I don't understand the question. Perhaps you could explain your issue in more detail?

tt2

There isn't a supported pathway from Youtube to iMovie. You would have to record the audio via a mic, or extract it by other means, and covert it in to a format that iMovie is compatible with. I believe there are apps on the app store that will do this.