Editing child theme help

Hi there,
I’m very new to all of this and would appreciate some (easy to understand for beginners) help please! I’ve just created a child theme in c-panel, and activated it. The child theme folder just has the basic style.css file in it, (i.e the basic code linking it to the parent css). I now want to edit CSS and customise it…but how do I do that? There isn’t code in the child theme style.css to edit…do I need to copy the css files from the parent folder and past into the child to edit? Thanks!