dose eny one now what a arduino is. If so then do you now how to use a serial?
I won't to know how to make a computer tel a arduino to tern the led on and off?
This is similar to what I used to create a "Mock" ECU ( http://en.wikipedia.org/wiki/Electronic_control_unit / http://en.wikipedia.org/wiki/Engine_Control_Unit ) to control a fictitious vehicle. I never got around to finishing that particular project.
I can't really be helpful with the specifics of your setup...but I'm sure you can find a tutorial for getting I/O to work with your hardware from the Arduino documentation. Try referring to the links at the end of that Wikipedia page for detailed tutorials.
to be more specific i wont to be abole to make a computer tel the arduino to move a servo like the arrow keys to move the servo.
*To *I *want *able *tell *with the arrow keys
Seriously. This is ridiculous. I'm sorry ty, but I really won't continue helping you unless you improve your grammar/spelling. I know, no one is perfect, but are you even trying? Perhaps you aren't a native English speaker, in which case I apologize. Maybe you're an eagle and you have to peck each key out, and you're trying to go faster. Perhaps you're a vegetable and you have to use your tongue to type..
On this particular issue, I believe there's a lib available for arduino communication.