Confused about how to use wp_enqueue_style

wp_enqueue_style is a MUST to add your styles according to codex. But you don’t need to use your child or parent theme name anywhere.

<?php wp_enqueue_style( $handle, $src, $deps, $ver, $media ); ?>

The first param $handle could be anything, doesn’t matter what you put here. I can see you have used your theme name in there, it acts as an identifier so you can use anything. But, make sure they are unique in all cases. For example, if you use like:

wp_enqueue_style( 'athletica-style', get_template_directory_uri().'/style.css' );
wp_enqueue_style( 'athletica-style', get_stylesheet_uri(), array('athletica-style')  );

Here the handles are same, so you will see one of those css is added, not both.

I think you are familiar with other parameters of this function.

Note: It is not mandatory, but always a good practice to register the style using wp_register_style function.