How add background to the code?

You can’t add an image to a border. Some idea of what part of a design you’re trying to change might help – ideally with a link to a page that demonstrates the issue.

Thank you Esmi,

Please see to:
https://ghiasabadi.com

How add a image to sidebar?

Do you mean an image background? If so, which sidebar do you want to add it to?

Yes
I want the background image to come in sidebar.

Thank you esmi

Which sidebar?

Oh dear Esmi,
I had forgotten. This problem is solved.

Mr. Mohsen Ghiasi this method showed that:

border-left:240px solid transparent;
Instead of:
border-left:240px solid #e6ece9;

Thank you, and he.