You can ripen a peeled avocado by wrapping the peeled avocado tightly in cling film and place it in the refrigerator and it should ripen within an hour or at least during the day depending on how unripe it is.
You can also do the same with cut in half Avocados that need ripened.
Just put the wrapped Avocados into the refrigerator and they should ripen up after awhile.
You can check the Avocados for ripeness by prodding it until it's at the ripeness you desire.