All the information you need can be found here: https://codex.wordpress.org/Child_Themes
The important parts to get it up and running would be to:
Make sure the parent theme exists (the complete accesspress-lite theme in your case)
Create a unique folder name for your child theme.
Create a style.css file in your child theme folder.
/*
Theme Name: Your Child Theme Name
Theme URI: http://access-keys.com/accesspresslite/
Description: Accesspress Lite Child Theme
Author: Your Name
Author URI: http://www.your-child-theme.com
Template: accesspress-lite
Version: 1.0
Tags: blue, white, light, custom-menu, one-column, two-columns, three-columns, left-sidebar, right-sidebar, fixed-layout, fluid-layout, custom-background, featured-image-header, sticky-post, theme-options, threaded-comments, featured-images, full-width-template, custom-header, flexible-header, responsive-layout
Text Domain: accesspress-lite-child
*/
Make sure the Template line matches the parent them folder.
Create a functions.php file within the child theme folder. In that file, import your parent theme styles. Doing this instead of an @import in your stylesheet makes sure that the dependencies are met.
function child_theme_enqueue_styles() {
wp_enqueue_style( 'parent-styles', get_template_directory_uri() . '/style.css' );
wp_enqueue_style( 'child-styles',
get_stylesheet_directory_uri() . '/style.css',
array( 'parent-styles' )
);
}
add_action( 'wp_enqueue_scripts', 'child_theme_enqueue_styles' );
Note that as a child theme, any time you use get_template_directory_uri() you’re grabbing the parent theme directory. Using get_stylesheet_directory_uri() will give you the child theme directory.