Testing your arduino connection
Before you start using your tiny new computer (aka Arduino) you are going to run a test. Using the blink code, you will be able to see a simple physical output where a built in LED blinks from the board.
Before you begin, you will need the Arduino Software downloaded. Refer to the link below this post for instructions.
Plug your Arduino board to your computer using the USB cable.
Start the Arduino Software (IDE)
Load the Blink code by going to < File < Examples < 01. Basics < Blink.
This will open up the Blink sketch.
This will initialize the LED that is built onto the board as the output.
This will supply 5V to the LED. To turn it off, you simply replace HIGH with LOW.
Before you start this test, follow the instructions here: Installing Arduino