Step 1 - Draw a general layout

First, start with the outside walls. Just try to get rough distances at first – you'll adjust things later. These outside walls are all basically joined corner-to-corner, creating the perimeter of the building. Then, add the interior walls. These walls will create the skeleton for the rooms inside the building.

Watch this short video below.

Note: This video has no sound; it has captions pointing out the relevant steps (program version 2.1).