Hello,
The OEM folder needs to be prepared before installation by yourself (this is a little complicated, so you need to consult some tutorial on internet) ...
But you could use WinReducer OOBE integrated tool, if you want a simple way to integrate your software (Files & Folders).
Just for the record, in the next major version, there will be many interesting improvements for the WinReducer OOBE tool ...
Have a good day !