Image Processing using cuda

I have to do a project implementing background subtraction algorithm using cuda, I have Geforce GT430 graphic card, please guide me what steps should I follow from scratch.
thanks in anticipation.

Google for the topic and you will find many implementations. You may save some time implementing some of these using ArrayFire free GPU library.

there is the cubgs project on google-code and several others if you look for them.
@short could you please tell me how you would implement background substraction with ArrayFire?