Click the Edit button on an option, then click into the Content tab in the top left corner of the window that opens.
Here, you are able to add photos or floor plans of the specific product. If there is a floor plan associated with the building, but not yet associated with the product, you will see a button that says "Add File" where you can add your own content.
Once a floor plan is associated with a product, you have the ability to draw on the floor plan.