You only need a isometric image , still you can use no image if you are good at 3d scuplting, but basically IMO start by using the MCD edit tool, you can see how the images are formed also you can do full model there ( in the preview part), next is the Dashiva mapview where you place the MCD´s you create in a specific map.
what i explain in the video is a more advance part where you can use a image to your advantage to be more quick
Anyway try the basic , i can help if u need some. Still i think there are some help on the MCD edit / mapview in the forum