Need help with one column, no sidebar

I haven’t made a webpage in 2 years, so bear with me here!

I download a theme that I liked: Graphene

https://www.khairul-syahir.com/wordpress-dev/graphene-theme

Includes a one-column, full-width page template (since 1.0.5)
demo: https://dev.khairul-syahir.com/wordpress/single-column/

The instructions tell me to make a child theme, so I make that.
and the file loop-single.php to put in the child folder with the style.css.

Go to wordpress and activate the child theme. I lost my header image, but that’s not really a concern right now.

What do I do next? I feel like I need to edit another file in editor on the child theme.

Any help would be greatly appreciated!