The mounted virtual drive contains an installer file "Windows_10_IoT_Core_for_Joule.msi". Double click the file to start the installation.
The installer creates a new directory: C:\Program Files (x86)\Microsoft IoT\FFU\Joule which contains the Joule image file "flash.ffu".
Copy flash.ffu to the root of the WinPE USB drive you created in step 2 above. You will use this USB drive in the next step to install Windows IoT.
If the platform fails to boot due to an ACPI BIOS ERROR, return to WinPE and rerun the JouleInstaller.cmd. As part of the script, it should remove the file c:\windows\system32\ACPITABL.dat. If rerunning JouleInstaller.cmd does not resolve the issue, remove the file manually.