To create a new test fit start on your home screen and select the floor from the building list on your left side then click the floor plan on the middle of your screen.
From there you will then enter a new view which will show you the floor plans template as well as any older test fits that have been created/saved.
Hover over the floor plan template and click on the "Create a new Test Fit" button that appears.
From here you will then be brought into the test fit editor mode and will be able to begin editing your floor plan!