Border around all page content

Hello.

I’m currently using the Shamrock theme for my site located at forkandhoehomesteaders.com. I’m wondering if I can create a border around the header, menu and all page content. An example would be this site:

https://www.loveandlemons.com/

See the border that runs down the side of the page on the left and right of the blog? I’d like something similar. Can you help me to find a way to duplicate those vertical bars or is this not possible with Shamrock?

Thank you