Locate the nut holding the alternator to the curved adjustment arm. It is usually directly under the alternator or on the side nearest you. Find a socket that fits the nut and push it onto the end of a socket wrench. You may need to use an extension on the wrench to reach the nut.

Set the ratchet so that it engages when you push the handle counterclockwise and unscrew the nut until you are able to pivot the alternator. You may need to hold the end of the bolt on the other side of the adjustment arm with a wrench to prevent the bolt from turning with the nut.

Place a long metal bar on top of the alternator and push it in until the end engages with a solid part of the engine. Push down on the end of the rod to force the alternator outwards, tightening the fan belt.

Reverse the ratchet direction and hold the rod down while you tighten the adjustment nut. Torque it as tightly as you can, then remove the socket wrench and the rod. Test the tension on the belt. It shouldn't move more than half an inch when you pull up on it.