Install 

1. you must install "Graphviz":http://www.graphviz.org/ in your system before you use it.

2. unzip the DCWorkflowEditor to your zope Products directory.

3. check if your dot binary path is included in 'bin_search_path' in config.py. 
   if not, add it. (on windows, it looks from registery automatically)

4. restart zope