The best option for writing your report is Latex. If you really want to use Word, you can use this Word template document, but you will almost certainly regret this choice in the latter stages of writing your report.

LateX is the choice of most CS academics in writing papers. It will save time in the long run, and it typesets beautifully. See here for a template and more information. You can edit and share your report using Overleaf (we have a subscription), which is an excellent way of sharing your progress with your supervisor.

These templates are based on those we provide to undergraduate students. The information in them may not apply directly to you.

For advice on writing the report, please see:
Report Writing Guidelines for BSc Students
This contains some excellent general advice, but note that it is aimed at an undergraduate audience and some details won’t apply to you.