To create a floor map or a seating chart for your event you need to select Reserved seating when choosing the event type. Doing so will reveal the additional settings for events with Reserved Seating.
With the (New seating chart) button you can create new charts or seating plans. Once created they will be available to choose from your list for use with your events.
Here’s some more info on building your own seating charts and floor plans:
Once you are happy with the floor map or seating chart, simply close the chart builder. If you need to change to a different chart press the choose from your list button. Then press Create event to complete the initial setup of your event.