How to create a vertical line between sidebar and content

Hi! I am working on my first website with WordPress: http://www.kindredcats.com
My current theme is “Delicate”. I have a 2 questions…

I would like to create a vertical line that separates the sidebar with the main content area of the pages. Is there a way to do this?

Lastly, I created an file in photoshop with my logo and some photos. It’s a very wide image, and I noticed that it is not “responsive” like the rest of the site. Is there any way to make it responsive?

Thanks!