Well, pretty much forget anything you've read in this thread so far.
The I4 alternator is held to the engine block with one long bolt that passes through the mounting holes on both sides. This allows it to pivot forward and back. At the top, it is attached to a slotted L-shaped bracket which has a bolt passing through it's end. When you tighten the bolt, the alternator is pulled away from the rear of the engine block, tightening the belt. When you loosen the bolt, the opposite occurs.
Of course, the alternator is located on the passenger side of the car, right below valve cover level at the back of the engine. It has to be removed from below if you are planning to replace it. It shouldn't be hard to spot an alternator...
And what's more, you should be properly adjusting the belt deflection by measuring the span between the two pulley centers (alternator and water pump) and looking up the corresponding deflection measurement. It's in my Haynes, but it's outside and I'm too lazy to go get it. To this, you need two rulers or a ruler and something else similar. Lay the flat thing or ruler across the two pulleys, and use the ruler to depress the belt in the center of the span with reasonable force. The measurement between the straight edge and belt which has been depressed is the deflection. A loose belt will obviously deflect more than a tight one, and will have a tendancy to slip and squeal like it is.
And there you go