to prepare coolant use distilled water or filtered water or atleast boiled ac drip water. Mix with equal parts of caltex coolant and pour in slowly.
Before this - you should have already drained the radiator and block, If there is no block drain - e.g. you own a cheapie japanese car, you need to remove thermostat valve and blow air through it to completely empty the system.
@ cheap coolant person,
Buy a large bottle of NASA coolant and use as recommended.