Base WordPress child theme functions file to load in both styles sheets from parent and child.

functions.php

<?php
/**
 * Child functions and definitions.
 *
 * @link https://codex.wordpress.org/Functions_File_Explained
 *
 * @package child
 */
if ( ! function_exists( 'child' ) ) :
add_action( 'wp_enqueue_scripts', 'enqueue_styles' );
function enqueue_styles() {
    // Check that we are a child theme.
    if ( is_child_theme() ) {
      // Load parent CSS. Noting the use of `get_template_directory_uri()` to get the parent themes path.
    	wp_enqueue_style( 'parent-style', get_template_directory_uri().'/style.css', array(), '1.0.0' );
    }
    // Load our child's CSS. Remembering to add our parent file as a dependancy to be loaded before.
    wp_enqueue_style( 'child-style', get_stylesheet_uri(), array('parent-style'), '1.0.0' );
}
endif;