How to Hide the "Pixobe Coloring Book" Admin Menu

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

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

Where do I put this code?