Reduce width of Side Bar pr remove completely

Is there any way of, at least, reducing the width of the sidebars in Sydney Pro or, better still, removing them completely?

Would I need to create a child theme (whic, as a newbie, I’ve never done) to achieve this.

It’s just that they are far wider than I’d like.

Thanks in anticpation.

V.

EDIT:

Solved it using CSS posted on this site for removing sidbars from all pages EXCEPT the blog page.