via web browser and open your already created File which you want to export to the local storage.
In your address bar you will get this kind of link:
How to export Figma File to JSON
Run your desktop Figma application, open any Figma file, and run DesignKit plugin. Go to "Export" tab, select Figma sub-tab, enter File ID and your generated token, and click on EXPORT button.
In a while, your Figma remote file will be exported to a JSON file on your local storage.
If you want to import the exported file, you can use