Activate button and LED flash

Hello everybody, I'm having trouble making a seemingly simple system, but would like your help.

The thing is, I need to push a button push him send a drive command as if pressing a keyboard key, basically this button replace a keyboard key. And so push the button, and send the command to the button, he would light an LED to blink for three seconds.

I am a beginner with the Arduino and would like some help with the code for programming.
Thanks.

The thing is, I need to push a button

Pushing switches will prove far more effective. How is the switch wired to the Arduino?

him send a drive command as if pressing a keyboard key

Which Arduino do you have? Not all Arduinos can emulate a keyboard.

And so push the button, and send the command to the button

Switches are input devices. You can't command an input device.

You have no code? - Scotty

PaulS:
Pushing switches will prove far more effective.

button
noun, but·ton often attributive \ˈbə-tən\

: a small part of a machine that you push to make the machine work

Merriam-Webster

aarg:
button
noun, but·ton often attributive \ˈbə-tən\

: a small part of a machine that you push to make the machine work

Merriam-Webster

Since the complete description of the hardware is "push-button switch", and button and switch are both the same length, why would anyone abbreviate the name to button, when switch is FAR more descriptive? In fact, the type of switch is often completely irrelevant. So, why is it so difficult to say switch when you mean switch, and leave buttons for shirts?