It could become very important for you to prove you have done this if there were an accident for which you or your group were potentially liable.
If you have not filled in a risk assessment before, this is a form you can use to help structure your risk assessment.
It is just a helpful checklist to help you identify and assess risks. There might be other risks, and you will need to add these yourself. The assessment is not complete until you have identified all the risks and what you will do about them.