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.
Footer Widgets
The spacing option for the footer widget will be available when you activate the Footer Widgets addon from Appearance > Astra Options > Footer Widgets.
To access these settings navigate to Appearance > Footer > Footer Widgets. Footer Widgets Padding will add padding for the footer from all sides.
Note: To add widgets to your Footer, navigate to Appearance > Widgets and add the needed widgets to the Footer Widget Areas.
Footer Bar
It will add padding to the main footer (copyright area) from all sides.