Nano V3.0 ATmega328P

So I bought this microcontroller to simulate a push button action.
Since I'm new to this how can I program it to work?

Run down,
I have a mini computer connected to a multimedia box and with the box has a button to change video source input, which the button has 2 wires +,- so Every time I turn my car on I have to push the button to change the video input to the computer, since it's a hassle to do it all the time, I ordered the Nano V3.0 ATmega328P to automatically push the button Every time the car turns on.