Lets say you need to calculate and illustrate areas that are existing and new for instance. Go to View... New... Area Plan and select the type of area (Gross or Rentable) and the level you want to apply the area calcs to. It will then ask you if you want to automatically create area boundary lines or if you would rather draw them yourself. Make a choice then go to Drafting... Area Boundary and you can edit the area boundaries yourself. Go to Drafting... Area Tag and you can tag each area in much the same way that you would tag rooms.
After you have your boundaries and tags placed go to Drafting... Color Fill and drop a color fill legend onto the view. You can now select the color fill legend and Edit Color Scheme to show areas by SF, Type, Name, or Perimeter.
Go to View... New... Schedule and you'll notice that you can now schedule your Gross and Rentable Areas.