As he prayed, God was touched; God listened and brought him back to Jerusalem as king. That convinced Manasseh that God was in control.
After that Manasseh rebuilt the outside defensive wall of the City of David to the west of the Gihon spring in the valley. It went from the Fish Gate and around the hill of Ophel. He also increased its height. He tightened up the defense system by posting army captains in all the fortress cities of Judah.
He also did a good spring cleaning on The Temple, carting out the pagan idols and the goddess statue. He took all the altars he had set up on The Temple hill and throughout Jerusalem and dumped them outside the city.
He put the Altar of God back in working order and restored worship, sacrificing Peace-Offerings and Thank-Offerings. He issued orders to the people: "You shall serve and worship God, the God of Israel."
But the people didn't take him seriously - they used the name "God" but kept on going to the old pagan neighborhood shrines and doing the same old things.
The rest of the history of Manasseh - his prayer to his God, and the sermons the prophets personally delivered by authority of God, the God of Israel - this is all written in The Chronicles of the Kings of Israel.
His prayer and how God was touched by his prayer, a list of all his sins and the things he did wrong, the actual places where he built the pagan shrines, the installation of the sex-goddess Asherah sites, and the idolatrous images that he worshiped previous to his conversion - this is all described in the records of the prophets.
When Manasseh died, they buried him in the palace garden. His son Amon was the next king.
Amon was twenty-two years old when he became king. He was king for two years in Jerusalem.
In God's opinion he lived an evil life, just like his father Manasseh,
but he never did repent to God as Manasseh repented. He just kept at it, going from one thing to another.