1995 Buick Regal Owner's Manual - Page 227

If this light comes on, it means you're low on engine coolant. To Add Coolant If you need more coolant, add the proper mix at the coolant recovery tank. If the coolant recovery tank is completely empty, add coolant to the radiator. (See "Engine Overheating" in the Index .) Add coolant mix at the recovery tank, but be careful not to spill it. 6-19