Always put a heading and address is to the relevant person (if you are asked to report to a specific person).
Write a short introductory paragraph stating what you have been asked to do.
Then address whatever is asked for in the question and refer to workings in the appendix.
Have a short closing paragraph and then sign with a name (but do not use your own name).
Best is to do the appendix first (your workings must be separate from the report) but make sure you write appendix at the top of the workings, and that you write ‘report’ at the top of the report.
Look at the examiners own answers to a few recent past questions to see the sort of style of the reports.