no belts aren't a type of pulley
The 1989 Toyota Corolla serpentine belt can be tightened or loosen with the tensioner pulley. Pry to the left on the tensioner pulley until the belt is tight. Tighten the tensioner pulley.
To drive the belts
You release the spring tension on the tensioner, a pulley in the belt system who's only purpose is to keep the belt tight. Normally you can use a ratchet to move the pulley away from the belt, but some are adjustable and require loosening a bolt.
I'm assuming you mean a pulley, which is what the belts run on. If so, depending on which pulley the bearings could be bad or if it is the crankshaft pulley (big pulley near the bottom) the rubber could be getting bad.
If the belts are new and tight then one of the driven accessories is having bearing trouble, try to track it down by listening to where the noise is coming from and then with the belt off turn the pulley checking for resistance or side to side play.
Check to see that all belts are tightened to factory specs. Too tight or too loose and they will break. Check the alignment of the pulleys. One out of alignment will cause this. Check the tensioner idler pulley if equipped. Installing incorrect type belts will also cause this. Refer to the link below for the diagram. If you have a serpentine belt it replaces the V-belt in (3) of the diagram. If you have the upper smog pump fitted it is powered from the power steering pulley.
Put the new fan belts around the fan pulleys. Slide the top tensioner pulley upward. Tighten down the tensioner pulley when you have achieved the proper fan belt tension.
Squeaking belts are the result of improperly adjusted tensioners and pulleys. The belt slides over the pulley and squeaks. Using a lubricant would defeat the purpose. Also I'm not sure what affect wd-40 would have on the material the belts are made of. To get them to stop squeaking tighten them up. Make sure you use your manual and don't get them too tight.
Large drive pulley, small driven pulley = faster rotation but less torque. Small drive pulley, large driven pulley = slower rotation but more torque.
not likely
bottom of engine where belts go