The Floor Plans add-on records a property room by room — each room's name, dimensions, description, and its own image — and displays them together on the property page. If you have seen earlier documentation describing this add-on as a single image plus a title, note that it is a full room schedule: individual room sizes are the detail buyers ask for most often after price and location, and nothing else in FW Real Estate holds them. The core product stores a property's overall areas; this add-on stores the rooms inside it.
When the add-on is enabled, the property form gains a Floor / room plan card. Each row in that card represents one room and contains four fields:

Rows can be dragged to reorder, so the list can follow the order someone would actually walk through the property rather than the order they were entered.
The unit used for room dimensions is a core setting, not a setting of this add-on. Change it under Configuration → General → Localization → Room sizes dimension to keep room measurements consistent with the property's other area values.
Rooms appear as their own section on the property detail page, showing dimensions, descriptions, and images together. Where that section sits depends on the Information grouping setting in Configuration → Properties — accordion, tabs, or a plain list. A property with no rooms entered renders no section at all; nothing empty is shown to visitors.

To install this addon, open the Add-ons panel inside FW Real Estate. See Getting Started → Add-ons for details on free addons, paid addons, and site verification.