The coolant that you are looking for is the green 50/50 mix. To add coolant, start the car and get it to running temperature. Make sure that heat is on full blast and the climate control fan is running. Now, fill the fluid until it hits the full line.
--
FCP Groton

No modern cars have a radiator cap. The overflow bottle cap is where to remove and add coolant. Remember, do not overfill past the "full" line.
To get the cap off, place a shop cloth over the cap and gently grab the cap with a pair of chanel lock pliers and turn counter clockwise.

Your antifreeze will "work", but check the back of the lable for type of mixture and ingrediants.

Your next task is to find out where the missing fluid went. Is the radiator leaking? Is the heater core leaking? Is the headgasket leaking? If it has been over 2 years, you really should have the system flushed and new antifreeze added.

Klaus
--
The more I learn, the more I forget. So why learn?

So, The tank is where you add the coolant. If you go to your parts dealer, ask them to remove the cap and add the coolant. If you have a pair of water pump pliers, take the cap off with it. Make sure that you turn it counter clockwise to remove the cap.
I would get a 50/50 mix for all types of cars.