Removing padding around heading and body of posts

I’ve been trying to remove the padding from the right and left sides of my blog headings and posts. I’ve tried the following CSS edits, but they aren’t working. It’s currently about 4mm wide (the line between the heading and body extends further).

.site-header .inside-header {
padding: 0;
}

#main {
clear: both;
padding: 1.625em 0 0;
}

My website is: https://www.shannongianotti.com