Changing the alternator belt in a Mitsubishi is a fairly simple job that does not require any special tools or automotive know-how. The only thing unusual about this task is that the belt tensioner bolt, which (as its name suggests) keeps tension in the belt, is not a standard bolt, but instead a hydraulic one. This means that instead of turning it counterclockwise to remove the belt, you will have to turn it clockwise to compress the hydraulic fluid and ease the belt off the tensioner.
Open the bonnet and locate the belt tensioner. It will be just under the alternator, on the left side of the engine bay.
Use a socket wrench to turn the belt tensioner clockwise until there is slack in the belt that is surrounding the alternator pulley. Keep pressure on the belt tensioner.
Pull the old belt off the alternator pulley by hand.
Place the new belt onto the pulleys you removed the old belt from while keeping pressure on the belt tensioner.
Release the pressure on the belt tensioner.