How to enable auto updates of wordpress core, theme and plugins

Enable WordPress Core File Updates

define( 'WP_AUTO_UPDATE_CORE', true );

Add the above line of code to wp-config.php file.

Enable WordPress Plugins/Theme Updates

add_filter( 'auto_update_plugin', '__return_true' );
add_filter( 'auto_update_theme', '__return_true' );

Include above two lines of code to functions.php