Reconnect the two electrical connectors onto the new alternator.
Place the alternator belt back onto the alternator, and tighten the belt tensioner with a wrench or ratchet. Tighten the alternator belt to half an inch of belt deflection.
If you would like to be precise, place a ruler against the belt perpendicularly and see how far down you can push it. If you can push the belt down more than half an inch, tighten the belt some more; then tighten the lock nut to keep the belt tensioned.
Tips & Warnings
Check the condition of the alternator belt. If there are many cracks in the belt, replace it so that it doesn’t break while you are driving.