Generally, you just have to load windows installation media to your computer and point wizard to the root directory. However, Embedded version does not have RE components (same with it’s installation media).
Try to install ADK for Windows 7 ( 8.1 won’t work due to difference in components versions). Easier way, create a recovery media at any other fully functional Windows 7 machine – it should restore Embedded backups without issues.
Out of curiosity, what services are you running on Windows 7 Embedded or is it used by end users?