Reduce width ONLY the article (In a width template)

Dear,
I can handle it with CSS (but not too much).
I have a full width template, but for the blog articles only I need to reduce the width of the text (here is the layout I’m inspired by, https://thevision.com/attualita/lavoro-domestico/)
I tried with the css P or Body, both padding and margin, but in this way it also changes the content of the footer and header.
Can someone help me ?
thank you so much that I will be answered

• This topic was modified 7 years ago by Steven Stern (sterndata). Reason: moved from developing to fixing

The page I need help with: [log in to see the link]