You can find Content Spacing settings under Appearance Customize Spacing Content
You can set spacing for main container and primary container. Know more about the container here.
Main Container Padding
Space Inside Main Container will be applied as a padding to the container. It will allow you to manage space between page/post content and the container edges.
Main Container Margin
Space Outside Container values will be applied as a margin to the container.
Top space value will allow you to manage space between header and container’s top edge. While bottom space value will allow you to manage space between footer and container bottom edge.
Primary Content Area Padding
Space Inside Primary Container will be applied as a padding to the primary container. It will allow you to manage space between page/post content and primary container edges.
Primary Content Area Margin
Here you can set top and bottom margin for primary content area.
Here you can set margin for heading tags (H1 – H6) used in primary content area.