There is a water reservoir tank that goes to the radiator that you can add the water to.
To add water to the radiator on a new beetle, first remove the lower radiator hose. Then add water to the coolant reservoir.
When a car is hot, keep the car running and add water to the radiator. When a car is cold, you can simply put the water into the radiator.
You can add water to a radiator any time it is low on water.
Look for a radiator cap and add it there.Look for a radiator cap and add it there.
It is better to add premixed anti-freeze.
In most newer cars, you add it to the overflow tank instead; in some of them, it's next to impossible to add it to the radiator itself. You should only add water when the engine is cool (ambient temperature).
It is no longer necessary to add just water to a radiator in newer cars like the 2005 Malibu. An antifreeze that is half water and half antifreeze is usually best. Add the 50/50 antifreeze to the radiator overflow tank. It should be a plastic, see through tank hooked to the radiator.
If you are speaking of a radiator in an automobile, there is a plastic bottle on the side of the radiator, and it is marked for the fluid level; "ADD" or "FULL". The cap on the bottle will say "COOLANT ONLY" or words to that effect. Do not overfill. Older model vehicles you will add water to the radiator itself. Remove the radiator cap, slowly, and pour in the water. NEVER REMOVE THE RADIATOR CAP IF THE ENGINE HAS BEEN RUNNING! Wait until it cools down.
At the radiator or overflow tank. Do not add water, add coolant.
You should add a 50/50 mix of anti-freeze and water.
I have a 92 Ford F150 and the cap is on top of the radator, but you can also add water via your overflow since your over flow is up higher, it will still drain into your radiator.