First I will give you credit for trying. But trying to remove an alternator without knowing what it even looks like is a clue you may need some help.

To loosen the tensioner, you need a 17mm deep socket on the 3/8" ratchet. The longer the ratchet, the better leverage. See pic. Using the casted bolt (seen in the mirror), twist the tensioner to release the belt. Once the belt is off, then you can remove the two alternator mounting bolts. I assume there are only 2, that is all I see looking at my car. Good luck. James