How to change width of subtle theme?

I’m using the subtle theme which looks great now but I’d like to change the width of the page. Can you tell be the code I’d use to change that in my child theme? I have two columns. the widget one is fine but the left/ main column is way to wide for the info I want to post. My videos seem to get lost in it and I don’t want to make bigger videos.

Thanks

Also I have the code to eliminate the title and date of page posted but is there a way to keep the word “edit” on the page only so just I can see it? It’s much easier to click on it to edit the pages.

site is: https://onlineincomepartners.com/