none of my css is working in my child theme

It looks like the code you copied from is missing the part where your child theme styles are actually added to WordPress. It’s a little strange they skipped over this, mind you!

From the WordPress Codex article on child themes, you just need to modify your style enqueueing function so it includes this:

wp_enqueue_style( 'child-style',
    get_stylesheet_directory_uri() . '/style.css',
    array( $parent_style )
);

You’ll want to put that in your code directly after the wp_enqueue_style() call that is already there.

Unless there’s something else going wrong somewhere, that should be all that’s now required, but it might be worth looking through that Codex article to see if there’s anything else you might not have done yet.