1- first downlaod it(graphviz 2.38).
2- install org.graphviz.Graphviz-2.38-graphviz-2.38.
3- now add "C:\Program Files (x86)\Graphviz2.38\bin" and "C:\Program Files (x86)\Graphviz2.38\bin\dot.exe" to path like this video
note:in windows 8 you must use ; for path example: C:\Program Files;D:\Users;E:\file\