What code do you want to import? If it is the processdefinition.xml file, you should create a new empty processdefinition in the graphical designer and overwrite the processdefinition.xml file with the one you want to visualize. All nodes will show up in the left upper corner of the screen when you open the file, so you will need to drag them around and put them on a convenient location.
I will add a feature request in JIRA to create a wizard for doing this. The dragging around will be unnecessary when there is a proper layout algorithm that is able to calculate decent default locations for the different nodes. There is already a JIRA issue for this last feature AFAIR.
Regards,
Koen
