Setting a background

I am trying to set the background image of a div but nothing is working, is there a particular I have to do it?
Here’s the link for the post
SwordsKingdom

Hey there,

Please update the message to include your code.

When you enter a code, please precede it with a separate line of three backticks and follow it with a separate line of three backticks to make it easier to read.

You can also use the “preformatted text” tool in the editor (</>) to add backticks around text.

See this post to find the backtick on your keyboard.
Note: Backticks (`) are not single quotes (').