I believe that you can adjust the tension in your belts from either the top of the engine or from underneath the engine. I can only give advice on how to adjust the belts from underneath the engine, because this is the only way I have have done it.
To adjust the belts from underneath the engine, you first need to be able to safely access the the underside of your engine with some room to work. The tools that you need are a set of metric wrenches and a set of metric sockets (I'm not sure what the exact sizes are, 8mm to 13mm should cover everything).
Once you get under your car, remove the bolts in the large plastic panel that is in between you and the belts, then remove the panel.
After the plastic panel is out of the way, the alternator should be hanging upside down on the lower right (passenger) side of engine just below the p/s pump. The alternator has two sets of mounts (feet) that are attached to two different brackets. The only mount we need to be concerned with is the adjustment foot (bottom mount). The adjustment foot is the single mount on the alternator that is facing towards the ground (It should be the one closest to you). Attached to the adjustment foot is the adjustment/swing bracket. Loosen (do not remove) the nut that runs through the adjustment foot AND the swing bracket.
Next, locate the tension bolt on the swing bracket that runs parallel to the swing bracket. Turning this bolt with a ratchet or wrench will allow you to adjust the tension in the alternator belt.
Note: You should not be able to twist the belt more than 90 degrees in any direction. Plus, if the belt shows signs of wear like cracks or missing threads, REPLACE IT.
Do not make the belt too tight. This may cause the belt to break, or damage the drive-end bearing in your alternator.
After the belt is tight enough, tighten the bolt that runs through the adjustment foot of the alternator and the swing bracket. Don't forget to tighten this bolt, or else your belt will become loose again.
Before you do anything else, you should start your car to make sure that the belt is not squealing. Rev it up slightly, like you would if you were accelerating.
If this solves your problem, reattach the plastic panel and that should do it.
If you need to adjust the tension in you A/C belt, leave the panel off and get back under the car.
The A/C belt adjusts at the idler pulley located below the A/C compressor. Both should be on the left (driver) side of the engine.
Once you locate the idler pulley, I am 99 percent sure you need to loosen the bolt in the middle of the pulley (DO NOT REMOVE THE BOLT OR THE PULLEY). If this is correct, which I am pretty sure about, you should be able to adjust the tension in the A/C belt with the bolt that is just below and behind the idler pulley. This is the same concept you used with the alternator belt.
Note: The tension and quality standards that apply to the alternator belt also apply to the A/C belt.
Once the belt is tight enough, secure the idler pulley by re-tightening the center bolt in the idler pulley.
Make sure the belt doesn't squeal and reattach the plastic panel.
If you have any more question, post them. I will check back tomorrow.Otherwise, good luck.