How to create content margin/disable floating text

Hi guys,

so I’m a real beginner, do not know how to code etc, but I’m keen to learn to set up my own basic website in the beginning.

You can find the website under: onebutler.co, wordpress theme is blankslate, as I was looking for a basic theme.
I’m already looking for solutions for 2 days now, so I think it’s time to ask the community for help.

First thing I want to change, as you may notice, the text border on the right side. Currently the text is just floating depending on the browser’s window size. I was trying to adapt the stylesheet, was working in the page’s particular code, but every change I did didn’t change the website’s look at all.

So again, my main goal is that my whole site content (logo, text, footer) is centered and has a margin on the right side.

I know this is maybe a 5 second fix for most of you guys, but I just do not know the exact name for my issue, that is why I probably couldn’t find it on google and in this forum at all. If you can help me, please also give detailed instructions about where to insert code exactly 🙂

Thank you in advance for your help!
Lucas