changed drivebelt, but still squealing

I have a 93 explorer that just broke the drivebelt. I'm new at this. I replaced the serpentine belt, but when I put it in gear something started squealing and the battery light came back on. Is there a problem with the alternator? It seemed to be hot and there was a burning smell. Can someone tell me if I should replace the alternator? The tensioner is supposed to be auto adjusting, so I don't think I can do anything with that...

Remove the belt and try to spin all the pulleys you see. Something will not turn smoothly. The pulley that will not turn is what caused the first belt to break.