The event details provide a general overview of your event...who, what, when, why and where. Write these down and be as specific as possible when answering them.
The clearer you are from the get go, the easier it will be in the long run. Try and include all possible details you can think of. I have included some examples below to help get you started. For instance, it is important to consider the timing of your event. When selecting the dates it is a good idea to check whether there are any other events already planned to avoid clashes. Also, it is a good idea not to plan your event on holidays or quiet periods when your event demographic may be out of town. Be sure to include your set-up and tear-down timing as you'll need your site/venue available during these times as well.
These are just some examples of proper planning details you'll need to consider.