To add a new area, select Diagram / Schematic / Add area. You will be presented with a dialog box that contains buttons for common area types. Select the button that most closely approximates the area you wish to create. That area will be added to the schematic. It will even contain a reasonable condition that will work in most cases when the data is configured in a way that Intersection Magic supports.
Note that that Add area dialog box contains a button labeled 'all'. Selecting this button places all of the 22 pre-defined areas onto the diagram. From here they may be edited or deleted as needed.