Basically, to edit the Ishikawa diagram, you hover over the area you want to change, an outline box normally appears and then you right click to get a list of actions
Chapter 14 in the Quality and Process Methods document in the JMP Documentation Library, details the platform.
Also, If you select the "?" tool from the tool bar, and then click on the diagram, the JMP Help system will bring up documentation on how to use the platform.
Jim