There is a good guide on Punto Sports I think.

But the question is, why do you need one? It's better to run your car off boost for the last couple of miles of your journey. As the car is moving, the air flow cools the engine better than just idling it on your drive where the warm air just circulates round the engine.

It's only once in a blue moon I use my turbo timeer and I only have it as it was part of my alarm.