Gutenberg editor

I have used Catch Responsive Pro for some time, but always with the classic editor. I have now started using Gutenberg editor but it only has a 580 pixel width for the content, which is really annoying and even worse than Classic for knowing where things actually are on the front end page. Is there a SIMPLE way to adjust this? Please note that I am not a developer of coder, so it really does have to be simple!!!