You should have a button on the steering wheel to turn it on, as per the picture. Click that first and ACC is activated, can then hit set to set the current speed. +/- then increases to the nearest 5 mph ie. 40-45-50 etc. using set/Res increases by 1mph in either direction.
If you turn on ACC should be on automatically next time you start the car. Whilst using ACC if you hit the active/deactivated button it cancels the current set speed. Press again to deactivate ACC completely.
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