Tips on Customizing WordPress Books Gallery

How to Hide WordPress Books Gallery Admin Menus

function plt_hide_wp_books_gallery_menus() {
	//Hide "WBG Books".
	remove_menu_page('edit.php?post_type=books');
	//Hide "WBG Books → All Books".
	remove_submenu_page('edit.php?post_type=books', 'edit.php?post_type=books');
	//Hide "WBG Books → Add New Book".
	remove_submenu_page('edit.php?post_type=books', 'post-new.php?post_type=books');
	//Hide "WBG Books → Categories".
	remove_submenu_page('edit.php?post_type=books', 'edit-tags.php?taxonomy=category&post_type=books');
	//Hide "WBG Books → Tags".
	remove_submenu_page('edit.php?post_type=books', 'edit-tags.php?taxonomy=post_tag&post_type=books');
	//Hide "WBG Books → Book Categories".
	remove_submenu_page('edit.php?post_type=books', 'edit-tags.php?taxonomy=book_category&post_type=books');
	//Hide "WBG Books → General Settings".
	remove_submenu_page('edit.php?post_type=books', 'wbg-core-settings');
	//Hide "WBG Books → Gallery Settings".
	remove_submenu_page('edit.php?post_type=books', 'wbg-general-settings');
	//Hide "WBG Books → Search Panel Settings".
	remove_submenu_page('edit.php?post_type=books', 'wbg-search-panel-settings');
	//Hide "WBG Books → Book Detail Settings".
	remove_submenu_page('edit.php?post_type=books', 'wbg-details-settings');
	//Hide "WBG Books → API Import".
	remove_submenu_page('edit.php?post_type=books', 'wbg-api-import');
	//Hide "WBG Books → Usage & Tutorial".
	remove_submenu_page('edit.php?post_type=books', 'wbg-get-help');
	//Hide "WBG Books → Contact Us".
	remove_submenu_page('edit.php?post_type=books', 'wp-books-gallery-contact');
	//Hide "WBG Books → Support Forum".
	remove_submenu_page('edit.php?post_type=books', 'wp-books-gallery-wp-support-forum');
	//Hide "WBG Books → Upgrade".
	remove_submenu_page('edit.php?post_type=books', 'wp-books-gallery-pricing');
}

add_action('admin_menu', 'plt_hide_wp_books_gallery_menus', 1000000000);

Where do I put this code?

How to Hide WordPress Books Gallery Meta Boxes

function plt_hide_wp_books_gallery_metaboxes() {
	$screen = get_current_screen();
	if ( !$screen ) {
		return;
	}

	//Hide the "Book Information" meta box.
	remove_meta_box('wbg_book_details_link', $screen->id, 'normal');
	//Hide the "Book Cover Image" meta box.
	remove_meta_box('postimagediv', $screen->id, 'side');
}

add_action('add_meta_boxes', 'plt_hide_wp_books_gallery_metaboxes', 20);