tell me how close the car outside with the engine running. I have a Fiat IDEA 1.3jtd. no alarm, central locking only

I assume you wish to leave it warming up in cold weather.
You'll need both keys. If one is a remote key, and the other is a non-remote, use the non-remote to start the car.
Start the engine with the "spare" key.
Lock the car with the remote as usual.

In the UK, it is illegal to leave a car unattended with the engine running, unless on private property. You'll need to check your own local laws.

Despite being locked, someone could still just smash a window and drive away.

thanks for the answer on my car this way does not work. in our country in the winter climatic conditions such that sometimes you have to close the car with the engine running)), otherwise will have to call a tow truck and auto warm day in a warm box)