but I really don't know where to start
In which case I don't think you are ready for this project. Do some of the tutorials first, like :-
http://www.arduino.cc/en/Tutorial/HomePage
Learn how to flash an LED, how to read a pot, how to make a pot control the flashing of an LED. Then you will know enough to be able to make sense of my answers.
It is a bit like learning in a foreign language how to ask for directions to the train station. It's all well and good but useless unless you can understand the reply. 