This is a premium feature available with Astra Pro Addon plugin. To use these Pro features, you need to have the Astra theme along with the Astra Pro Addon installed on your website.
You can manage the spacing using the Spacing module available with Astra Pro. Please refer document, to begin with, Spacing module.
Make sure you have activated the module from Appearance > Astra Options > Spacing.
It provides a spacing option for Footer Widgets as well as Footer Bar.
Spacing option for footer widget will be available when you activate Footer Widgets addon from Appearance > Astra Options > Footer Widgets.
Footer Widgets Padding will add padding for footer from all sides.
It will add padding to the main footer (copyright area) from all sides.