Adding a valve to switch off the water to your outside tap

How to add a valve onto a pipe so that you can turn off your outside tap in winter. Also applies to adding any on/off valve to a water pipe in the house.
Be aware that you should always have a non return valve (check valve) in an outside tap somewhere. A lot of taps have this built in now but not always. In this video I already have a non return valve in the tap. If you don't then you should consider adding a check valve at this point as well.