The above is correct, but be aware that the previous owner (if there has been one) may have drained the G12 coolant and replaced it with standard coolant, in which case adding G12 is not what you want to do. Look at the colour of the coolant already in there, and if it's pink then you're probably still running standard coolant. It it's green or orange (or brown) then it will need flushing and refilling.