Your ABS system has sut down because a fault has been logged in the system
. The only way to sort this is to have the fault codes read (scanned) by a suitably equipped garage with the relevant diagnostic equipment (it doesn't have to be a dealer).
Have you done anything to the car recently in the area of the brakes or suspension? Is there anything else that has happened that could give a clue to this (driven through flood water, had new tyres fitted, etc). Anything at all might help.