You can start modeling without any reference, however, if you model on top of a turnaround reference sheet, the final result would be better, it also ease the progress of modeling.
The recommended features for reference sheet in Dust3D:
* Only one image, but include at least two profiles in the image, one for front view, one for side view. And align horizontally with the same height.
* Image size less than 1MB. Because if you save the document, the reference image will also be included in the .ds3 file.
* No blur filter, make a clean sheet, Dust3D will blur it for you when you load the image.
The above reference is a good example. The raw picture comes from https://www.antweb.org/bigPicture.do?name=casent0103346&shot=d&number=1 Composed in GIMP.
Modeling in Dust3D
=====================
#. Load Reference Sheet from Menu: File > Change Turnaround...