Arduino Duemilanove not uploading

Hi my Arduino Duemilanove ATMEGA 328 is not loading up. I know is because I do not have it on the correct serial port. Every time I try to upload anything to it I get a message saying "Serial port 'COM1' not found" I have looked at other post but nothing has helped. I am working on a Mac Os X version 10.6.8 and I do not know how to make my Arduino work. When I go to tools >>serial port.. I do not see any usb chooses there how can I add them so I am able to upload my board. PLEASE HELP :~

The Duemilanove needs the FTDI drivers installed, download the appropriate drivers for your OS here: http://www.ftdichip.com/Drivers/VCP.htm