You will have to remove the plastic on the bottom of the bumper and under the engine.. and either remove the lower radiator hose or it might have a drain that you can turn usually by hand.

It seems a bit early to be replacing coolant. The modern stuff usually lasts 5 years or 150k miles.

You can pick up a very inexpensive tester at the auto parts store.

You don't need to change the coolant now. Leave it alone. 

The overflow cap is likely the radiator cap.  Most cars are going in that direction. 

The overflow holds pressure just like the radiator. And that is where you refill after draining the coolant.

The drain valve should still be in the lower radiator on the driver's side.

I have always just drained what came out of the radiator and refilled it with 50/50 coolant.  Never had an issue.

OK, let’s locate that radiator, first: … open the hood, prop it up, look to the right off centre: … there is that doohickey with printed label on it, says: "DANGER! HOT, … do not open when hot!" That’s a radiator cap, … radiator is right beneath it … that large, vertically placed rectangular box! If you lean over, and look down, you will see two cooling fans bolted to that vertically mounted box. Success, … you now know how to locate a radiator in pretty well every make of a car!

Now, … draining it: … crawl under the bumper, under the car, look for the cut out in plastic shield, … right under that rectangular box you located before - radiator - there is a cock with butterfly-like wings. That’s a drain plug. Don’t touch it! Don’t use it to drain the radiator. That part breaks, leaks after, leave it alone! There is easier way to drain the radiator! There is large hose attached to the bottom tank of a radiator. You disconnect that hose to drain the system, … trust me! [… btw, you will have to remove that plastic shield underneath to access a hose connection - not a daunting task!]

Now, to check the coolant level: You do that at the expansion tank, there are two markings: LO and HI. When the engine is cold, level should be just above a low mark. If the engine is hot, level should be just below high mark. If that’s where it is. You’re done, … level is fine. [ … btw, that expansion tank is connected to the radiator with a rubber hose, connection is just below a radiator cap, right at the neck of filler opening!]

Next, … draining, flushing it out, refilling it: … just search for a vid. Scotty has an excellent one, … others, too! View them, … think about it, view them again. You should be able to do it just like a pro, … er, almost! Good luck.

Best,

F.S.