Start by making an Area 'Scheme':
Go to Home> Room & Area and click on the down triangle.
Select, Area & Volume computations.
Click on New and create a new area scheme and call it what you like. Choose 'Rentable' or ' Gross' (they're usually Rentable).
Now we need to create a new Area Plan. Go to View>Plan Views>Area Plan.
Select the Area Scheme you've just created and the new plans you want to add (i.e. Level 1) and select your scale. It's best not to duplicate views as any duplicate views in the same area scheme will override the other.
When the following prompt appears, select No.
Now you'll need to create areas using Area Boundary Lines. Under Home>Area> Area Boundary Line.
UNTICK the Apply Area Rules button. You'll have to do this each time you draw a new boundary line (which is a little annoying).
Sketch your area boundary.
To add an Area go to Home>Area>Area. This is similar to adding a Room. Area Tags can be turned on or off under Visibility Graphics-Annotation Categories.
On your plan, name your areas what you like, i.e. OFFICE AREA, CORRIDOR etc.
If you want one, add a legend, under the Home tab>drag on a Legend.
Select your Area Scheme and Colour Scheme.
If you want to change the legend colours, click on the Legend in plan, then select Edit Scheme.
Set up a schedule to show areas, including calculated areas.
View >Schedules>Schedule/Quantities.
Select from Areas category.