Margaret, undi the metal cap with a coin. The tube with the rubber end will fit over a normal tap. The other end of the tube which has a piece of plastic shaped like a trumpet fit into the hole where the metal cap protects. Ensure you have this over a sink for when you begin to run water from the tap. The water goes down the tube and come back out again through the trunpet part into the sink thus descaling the iron
Jamesey
April 2011