Once you have opened Detect3D
Click the open folder icon or select File -> Open Project from the menu.
In the window that appears, navigate to the location of the Tutorial 4.d3d save file
Select the Tutorial 5.d3d project file and click Open. A small window will appear showing Detect3D importing all the detector coverage regions, contours, and isovolumes.
Upon completion the following window will appear.
The project has now been loaded, if any contours or isovolume are visible, toggle their visibility off by deselecting the checkbox next to each name before continuing.