Welcome in Arduino land.
Please take some time to go throught the tutorial section like - http://arduino.cc/en/Tutorial/Button
- as there is a lot to learn. IN a few days you will learn a lot, and although the sketches may seem simple there is a lot of know how in them.
(you will find the answer to your question in the above link)
Another site with good tutorials is ladyada - http://www.ladyada.net/learn/arduino/
For more know how about electronics - http://openbookproject.net/electricCircuits/
Have fun, and if there are questions just let us know.