First plug in your usb to serial adapter and find the devicename using the Terminal program, mine is listed here:
ls /dev/tty.* /dev/tty.usbserial-AH06ORK9
Then start the screen command with the devicename and baudrate
screen /dev/tty.usbserial-AH06ORK9 9600
If you want to keep a log you can do so with
When your finished exit with :
Thanks Jeff Huckaby at Rackaid for this nice post.