First you actually have to give an opinion like 'I loved it' or 'I hated it' and then the reasons are like 'because I did....' or 'because I went....'. It's basically trying you to describe what happened but in a more analytical way.
You choose a holiday, and put what you think about it. Where it says MY OPINION (main idea), where it says reason #1,2,3 you put what you think about that holiday. To back up your main idea.