The first step is to refer to the owner's manual to see how often to replace the cooler or heater. Most say every two years. Standard coolers were fine for a range of about thirty thousand miles, but now there are even some that claim to last up to fifty or even a hundred thousand.  You can visit some site like https://www.hotheadheater.com/ to get the required information on replacing cooler or heater.

Next, you need to make sure that you have the correct cooler that will meet your automaker's specifications. Every local car dealer should have what you need. You can also purchase drip pans for the old cooler and empty containers for mixing the new cooler with water at the store. 

The next step is to prepare your car for takeoff. The first thing to do is to let your car cool down for a few hours before trying it out. Always park near the hose and certainly not on a hill. You can turn the ignition just enough to turn on the temperature display. When it says it's cold enough, just turn on the car heater and remove the ignition.

You can then drain the old coolant. Look for the radiator cap, which is usually on the front, and a sign of engine coolant. With the drain pan in place, pull the plug at the bottom of the cooler. Some of them can be developed by hand or with a wrench. Some may even need special customization tools to work. 

Then put the plug back in the bottom of the cooler and make a mixture of fifty and fifty with the cooler and water. Fill the cooler completely and half fill the tank if you have one. Turn on the engine and heater in your car, and monitor the gauge to make sure it doesn't overheat.