How to Hide the "Blocksolid 1" Admin Menu

function plt_hide_blocksolid_menus() {
	//Hide the "Settings 1 → Blocksolid 1" menu.
	remove_submenu_page('options-general.php', 'blocksolid.php');
}

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

Where do I put this code?