Expanding the middle area of your template?

I am still a newbie to blog building but I want to figure out how to expand the middle section of my blog because I want to enlarge the pictures on my blog, when I try to do so it bleeds into the right hand side of my site, I want to expand it to the left side where its blank so I can add larger photo’s, here is my website for an example https://www.joannalynnphoto.com , if anyone can help it would be greatly appreciated.