How can I change 16'; tires to 14'; tires on my car?

You need to get the right size wheel, both diameter and width. Then just put tires on and mount them on your car.How can I change 16'; tires to 14'; tires on my car?
buy 14'; rims and tiresHow can I change 16'; tires to 14'; tires on my car?
yes, but it will look stupid
with tools.
Buy 14'; wheels and tires that have the same lug nut pattern as your 16'; wheels.
Buy some 14'; tires then put them on. Don't forget to get your speedometer recalibrated.
Need new tires and rims however when you buy keep in mind to ensure the width, lug pattern, and offset are correct for your car
BUY A NEW SET OF RIM AND TIRE, MUST MATCH THE EXIST HEIGHT OF THE TIRE, SO THAT THE SPEEDO WOULD WORK ACCURATELY.
By finding 14'; rims with the same bolt pattern that will fit on your vehicle. Then buy tires that will fit the rims. Now be aware that your speedometer will be off. Also be aware that your vehicle wasn't designed to run on those little bitty tires, and that the suspension may be off, that the car will be lower and there could be damage, lots of reasons not to do it. But if you really want to...
Do you have wheels already mounted in your 14'; tires? If you do then take the T bar normally found in your trunk and unscrew your lug nuts. Pull the 16'; tires off and pull the 14'; on and screw the lug nuts back in. Make sure to screw them tightly and rotate the tire as you go. Make sure its weight tight, meaning its tight enough by using your body weight. If you dont have a jack or somewhat weak to unscrew the lug nuts take the tires to a car shop where they can do it for you. You can probably get a balance done while at it.
Go to an expert for advice.

Have you thought of why the manufacturer put 16'; tires on you vehicle.