How to set outer spacing:

To set outer spacing of background, first click on design mode. Next, click the spacing tab and choose a zone. Then, hover over the zone and click the pencil icon. After, choose override.  Then, click the sides you desire and type in the pixels or use the slider.

Here is how to set outer spacing:

Step 1: Click the design tab. 

Step 2: Click Spacing tab (A). 

Step 3: Choose a zone (B). 

Step 4: Hover over the zone and click the pencil icon (same as editing a widget)

Step 5: Choose override (in red)

Step 6: Click the sides you desire (C). 

Step 7: Type in the pixels or use the slider (D)