style.css

/*
 Theme Name:   Twenty Fifteen Child
 Theme URI:    http://example.com/twenty-fifteen-child/
 Description:  Twenty Fifteen Child Theme
 Author:       jaspreetdeveloper
 Author URI:   http://jaspreetdeveloper.com
 Template:     twentyfifteen
 Version:      1.0.0
 License:      GNU General Public License v2 or later
 License URI:  http://www.gnu.org/licenses/gpl-2.0.html
 Tags:         light, dark, two-columns, right-sidebar, responsive-layout, accessibility-ready
 Text Domain:  twentyfifteenchild
*/

                                                     functions.php

<?php
add_action( ‘wp_enqueue_scripts’, ‘my_theme_enqueue_styles’ );
function my_theme_enqueue_styles() {

    $parent_style = ‘parent-style’; // This is ‘twentyfifteen-style’ for the Twenty Fifteen theme.

    wp_enqueue_style( $parent_style, get_template_directory_uri() . ‘/style.css’ );
    wp_enqueue_style( ‘child-style’,
        get_stylesheet_directory_uri() . ‘/style.css’,
        array( $parent_style ),
        wp_get_theme()->get(‘Version’)
    );
}

                                                            or

Copy screenshot from parent theme to child-theme folder.