need few line of code in function.php
There are two ways.
1. Custom code in function.php
add_action( 'feed_links_show_posts_feed', '__return_false', - 1 );
add_action( 'feed_links_show_comments_feed', '__return_false', - 1 );
remove_action( 'wp_head', 'feed_links', 2 );
remove_action( 'wp_head', 'feed_links_extra', 3 );
2. Using EC Addons
