Events are typically used for creating minimum and maximum night stays, but also have other uses, such as enforcing special rules for specific date ranges, such as holidays or blocking availability due to park closures/events.
To create an event:
In the main settings cogwheel, go into Reservations -> Events.
Click on the Add/Plus button in the upper right corner to start creating an event.
Enter in a name fore the event, and click Save.
The following screen that displays is the Event Properties/Settings screen. Enter in any information that is relevant to the event that you are creating. You do not need to fill in every box.
After inputting the settings, click on Dates at the top. In here, you can add in the dates where this event is enabled.
When everything is set, be sure to save!