One of the most frequent questions to use python scripts in gimp is where to store the .py
files, just look in the preferences gimp directories assigned to it or assign a new one:
From the Edit menu, select the Preferences
option that opens the preferences dialog box, in the list to the right and look deploy Folders Plugins, can save the files in any of the directories listed in that entry or assign a new directory.
To view the scripts added in the menu you need to restart Gimp.