Abstract: If you wish to use GroupPolicy (*.admx templates) locally without AD (e.g. for testing or for PCs which do not an ad join) you can copy and use the files locally. The following steps are needed.
In this short howto we will use the Microsoft Office 2016 Administrative Template files (ADMX/ADML) on a local PC which do not have an AD join.
1.) Download the Microsoft Office 2016 Administrative Template files (ADMX/ADML) from the Microsoft Website and store them on the non AD joined PC
2.) run the *.exe and let the installer extract the files to C:\temp (create the folder if it didn´t exists before you run the *.exe)
3.) Copy all *.admx files from the folder C:\temp\admx to %systemroot%\PolicyDefinitions\ (e.g. normally C:\Windows\PolicyDefinitions\)
4.) open each language subforder in C:\temp\admx and copy the language files to %systemroot%\PolicyDefinitions\ (e.g. normally C:\Windows\PolicyDefinitions\). If we use an English OS as example you will copy all C:\temp\admx\en-us *.adml to %systemroot%\PolicyDefinitions\en-us (e.g. normally C:\Windows\PolicyDefinitions\en-us)
5.) Now you can run gpedit.msc and change the setting
5.) Reboot the PC to make sure your new policy could be applied
For more infos read: Editing the Local GPO Using ADMX Files