How do I replace a broken alternater belt on a 2003 mitsubishi lancer

First pop the hood and find the serpentine and alternator belts on the left side of the engine compartment. The serpentine belt runs around four pulleys. The alternator belt uses two pulleys. They share space on the drive shaft so they are right next to each other.
Of the four pulleys using the serpentine belt, three of them are vertically in line (closer to the front of the car) and the fourth stands alone (closer to the cab). Of the three vertically in line, the middle pulley is the one used to adjust the tension on the belt.
You must first break loose the bolt in the center of the tension pulley (the bolt is facing the passenger tire) by turning it counter clockwise. Then leave that bolt and go to the bolt connected frame connected to the other side of the tension pulley (this bolt is facing the front of the car). Turn that bolt counter clockwise until the serpentine belt is loose enough to pull off. Replace the belt and tighten in the opposite order. Once the desired tension is reached, crank the car and run it for a few minutes. Finally cut the car off and check the tension, tighten or loosen as neccessary.