New driver. How do I turn the car on with the engine off to use a mobile?

[CB72]

You can use the phone if it is in a dashboard holder whilst the engine/drive is live, the law isn't very clear for hybrids and EVs.

[ColinB]

You can use the phone if it is in a dashboard holder whilst the engine/drive is live, the law isn't very clear for hybrids and EVs.

Depends what you mean by "use". Read the rules:
https://www.gov.uk/using-mobile-phones-when-driving-the-law
So you can do what you like whilst the car is "safely parked", eg set the phone up for the journey and put it in a dashboard holder. But you mustn't touch it once you start the engine (or - my interpretation - turn on a hybrid/EV), you can only use it hands-free. And there's no logic in that if you have to use a touchscreen to control car functions (looking at you, Tesla).

[Jocko]

You can also use the built in touch screen without penalty, even scroll through several menus all legally.

There is also "Driving without due care and attention" so don't try the "but it's legal argument if you have an accident.