Wordpress Basic Links to Start up

Create a child theme in Wordpress

Go to this Link - https://codex.wordpress.org/Child_Themes


Register Menu In Wordpress
Code in functions.php file
Go to this Link - https://codex.wordpress.org/Navigation_Menus


Show Menu Front of Wordpress

Header footer or index where you want to show.
Go to this Link - https://codex.wordpress.org/Function_Reference/wp_nav_menu