Before you set up your trip you must have obtained approval from the DO to undertake it. The DO will make it easy for you and create the trip 'shell' for you from a past trip or from a clean trip template and they will also have given you access as an Event Official and set up the 'venue' if required.
You will know all the key facts about your trip to pass on to others: dates, times, meeting places, suitable diver grades, exercises, kit required, kit-hire, accommodation, food and catering, etc., etc.
As DM you need to try to fill the trip with members. But if it doesn't fill you need to open the trip to other clubs or tell the operator to open remaining places to the public. You need to determine that date in conjunction with the operator. This is the registration close date. After this date members must approach you to register for the trip if spaces are available.
Certain questions are asked for every trip, or at lease every trip to this site. These help you to assess participant risk. In general do not remove or modify these.
Add other fields necessary for the particular trip e.g. related to meals, accommodation.
Don't ask about standard member information already on the system: Emergency contacts, medical fitness, food allergies, diving qualifications.