During the last Intel® IDF in San Francisco, the Intel Joule board was presented supporting 3 different OS BSP: Ostro, Ubuntu and Windows 10 IoT Core.
For the first two OS the images was published at IDF time. For Windows 10 IoT Core the public image and support has published in mid October.
As all the other Windows 10 IoT Core images for other supported boards, the distribution is located in an unique site:
I'll try to graphically describe the step by step procedure that Microsoft publish to prepare and flash the board.
The previous link show the following page: