Coolant is a ready-made product - it's ready for use. Coolants are made by mixing antifreeze with water. It is necessary to add distilled or demineralized water to the antifreeze, usually in a 50:50 or 60:40 ratio in favor of antifreeze. The extent to which you mix antifreeze and water mostly depends on the climate conditions. It is best to follow the instructions on the package.

More on coolants/antifreeze is available in Advice & Proposals section.