[SOLVED] Make main content area wider

Could you let me know please how I would go about making the main content area of the template in the front end a little bit wider. I have a wrapper page that I want to fit horizontally, at the moment it gives me scroll bars, so just want to make the content area a little bit wider to fit it.
I tried setting it in the customizer to 1400 and that worked in the preview pain, but when I save it and applied that style it didn't pull through into the front end.

I ended up deleting the Style, re-created and daved it and this time it did apply to the front end.

Problem solved.