I’ve never owned a car with a “low coolant” warning light on the instrument cluster, but I suppose that feature might exist in high-end cars. The traditional method for checking coolant level is to get the engine up to normal operating temperature, then pop the hood and take a look at the coolant overflow reservoir, which typically has “MIN” and “MAX” marks molded on its side. If the level is between those marks, then you’re good. If it’s low, then you add coolant/water to the reservoir.
My experience has been that there’s no need to open the radiator for a look. Out of curiosity, I dug up the owner manual for your car (PDF file can be found on this page), and waddyaknow, on page 7-29, they do say to start with a cold engine and pop the radiator cap for a look. Which means:
This was a legit answer on their part, but better customer service might have meant someone telling you that you should check it periodically yourself in accordance with the owner manual (i.e. at least once a year).