Below are the steps to add subsections to a floor:
1. Select and expand the building with the floor where you want to enter subsections. See figure below:
In this case, the 4th floor is selected.
2. After
selecting the floor, click on the Add Subsection button 
and you will get the figure below:
3. Enter the details of the new subsection.
4. Click
on the Save button 
to save the new
subsection. Otherwise, click on the Undo button 
to cancel subsection entry.
5. Click
on the Close button 
to go back to
the Buildings List.
6. Repeat steps 1 through 5 for all other subsections you want to add.