Within the Email Template that you wish to edit, ensure the 'Layout' mode has been selected at the top of the page.

Hover over the snippet you would like to edit the spacing of and select the pencil icon.

This will open up the edit row window on the right-hand side of your screen.

In the 'Spacing' section, remove any 'Top' or 'Bottom' spacing which pulls through from the background of the row.

So it replicates the below spacing.

Now click directly on one of the columns within the snippet. Having clicked, you should see a new 'Edit row' window appear on the right-hand side of your screen.

Within this new 'Edit row' window, you can add in as much 'Top' and 'Bottom' spacing as you desire.

Now repeat the process on the other column. 

You can also add 'Left' and 'Right' spacing to increase the border edge.

You can repeat this process for each snippet that you wish to edit the spacing of.