How to Hide Pixobe Coloring Book Admin Menus

function plt_hide_pixobe_coloring_book_menus() {
	//Hide the "Pixobe Coloring Book" menu.
	remove_menu_page('pixobe-coloring-book');
	//Hide the "Pixobe Coloring Book → Pixobe Coloring Book" menu.
	remove_submenu_page('pixobe-coloring-book', 'pixobe-coloring-book');
	//Hide the "Pixobe Coloring Book → Settings" menu.
	remove_submenu_page('pixobe-coloring-book', 'pixobe-coloring-book-settings');
}

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

Where do I put this code?