In backend left-side menu click “Appearance” and then “Editor”:
You are not in the customizer, click “Styles”:
This takes you to the style-selector, click the edit-button in the op right. Looks like a pen:
This opens the style-editor in the right site of the screen:
Now click “Blocks”, this brings up a list of blocks you can customize, pick “Column”:
This brings you to an interface that lets you change the default design for columns:
You need to scroll to the bottom, open the “Additional CSS” option:
And add the code you see there:
.dropshadow {
box-shadow: 0px 0px 10px 0px rgba(0, 0, 0, 0.3);
}
Then click the “Save” button in the top-right corner:
Button changes a bit, just in case you changed your mind. Click it again:
Now navigate to the page and the column in the editor where you wish to add drop shadow:
And add “dropshadow” as a css-class:
Very pwetty and very phancey ?