Customizing WordPress themes is simple it just looks complicated. In this tutorial I create a basic child theme to customize the look and feel of the new Twenty Fifteen theme.
In this video I referenced the following WordPress Codex pages for information.
http://codex.wordpress.org/Child_Theme
http://codex.wordpress.org/Function_Reference/wp_enqueue_style
http://codex.wordpress.org/Function_Reference/get_template_directory_uri