From the documentation, it's pretty clear - the Help menu.
Enable JDev Extension - section 9 : http://docs.oracle.com/cd/E26098_01/install.1112/e17074/ojdig.htm#BDCBECBH
The issue was to find this menu - until I finaly found the empty entry right to the Window menu - It's the standard location for this entry, on Mac OS-X, except that it was not rendered due to the number of tools I have coming from the far right end.
As it took me some time to figure it out, I'll share it here in case you are running into the same small hurtle.
|Help menu, right to Window, but without the display name when space is limited.|
Once you have the extension installed, here is a good blog post that walk you through the next steps: