Why is my Kia Rio not starting after I put a new alternator in?

If your alternator was bad then it wasn't charging your battery. Put a charger on it and let it charge overnight. See if it fires up in the morning. If not post back and let us know.

I see Reeline's answer, and raise a better one: When an alternator goes bad, it can take out other components with it. Mainly, the starter, and the starter solenoid. Firstly, put oil in your car; it has nothing to do with this, but letting fluids get low will wreck your car, kill it. I see that you bought your battery in May this year. If you have a friend, and a set of jumper cables, there's a simple test: jump your car. If it starts, the battery is low. just let the engine run, drive it around, to charge it back up. If it doesn't start, but you can hear that electronic "click" when you turn the key, then the alternator took out your starter when it died. If it doesn't start, and there's no electronic "click" when you turn the key, then the alternator took out the starter solenoid when it died. Hope this helps!!

Also check battery connections. They must be tight and clean. Trickle charge battery overnight and it should fire up for you in the morning.

On Wednesday of this week, I took my battery into Sears to have it checked, and they said my battery was fully charged and working right, and my starter is a few years old, and if it was just my starter, why won't the car light up?

If you want to do a quick test, try this: If car is not starting, jack up the front end. Locate starter underneath. Have someone turn the key to the "ON" position like they're trying to start it. As they are holding the key to the ON position, rap on the starter with a hammer. If the car suddenly turns over, this means that your starter is bad and needs to be replaced.