You can create areas using 2 methods:
To create an area
See About Area Plans.
 Room & Area panel
Room & Area panel Area drop-down
Area drop-down
 (Area).
 (Area).  Tag on Placement panel
Tag on Placement panel
 (Tag on Placement).
(Tag on Placement). To omit a tag when you place the area, turn off this option.
If you place an area inside area boundaries, it expands to the extents of the boundaries. You can also place an area in a free space or one that is not entirely bounded, and then draw area boundaries later. The area expands to the boundaries.
To make the area visible in the view, click View tab Graphics panel
Graphics panel Visibility/Graphics. On the Model Categories tab, expand Area, and select Interior Fill or Reference (or both). See Override graphic display of element categories.
Visibility/Graphics. On the Model Categories tab, expand Area, and select Interior Fill or Reference (or both). See Override graphic display of element categories.