There are three sections on this page. To the right are the "Locations" which allow you to add and name the floor plans such as Main Floor, Property, Second Floor, etc. The middle section is for your images with a Floor Plan tab and a Photos tab. On the right is the Floor Plan editor.
To get started click the "Floor Plan" tab in the center image box. Click your floor plan and drag it to the appropriate level or location on the right. You can rename a location by clicking on the bar and highlighting the text. You can delete a location by clicking the red X. You can add a new location by clicking the "Create Location" button.
Once you have dragged and dropped your floor plan(s) into place you can begin to add your images to the floor plan. Click the floor plan location on the left and your floor plan will appear on the floor plan editor on right. Click the Photos tab. You can then click the photos and drag them into the appropriate spot on the floor plan on the right.
As you add the images you will see a camera icon appear. When you click the icon, the images will pop up.