How to Hide the "Easy Smooth Scroll Links" Admin Menu

function plt_hide_easy_smooth_scroll_links_menus() {
	//Hide the "Settings → Easy Smooth Scroll Links" menu.
	remove_submenu_page('options-general.php', 'essl-plugin-options_options');
}

add_action('admin_menu', 'plt_hide_easy_smooth_scroll_links_menus', 11);

Where do I put this code?