Do i need to add coolant to my radiator?

Just add to the reservoir when it is cold to the MAX line. Start the car and let it run and warm up. The coolant in the reservoir will be sucked into the radiator. Let it cool down and add back to the max line. I would find and fix the leak though as soon as you can or you will be continually be adding coolant. Running too low , you can overheat and be stuck on the side of the road.