You do NOT have to identify yourself. However, by entering your name and/or a way of contacting you, the club officer responsible for complaints will be able to get in contact with you and it may help in resolving the situation.
Even if you do choose to identify yourself, you may indicate that you would prefer to remain anonymous. In that case, the club officer responsible for handling these reports will not name you when discussing the case with other board members or with the people targeted by the report.
This report will only be viewed by the club officer elected to handle them. It will never be shown to any other member or officer of the club.