How to register unregistered land bought in 1995 legally?

My father purchased a plot in Kanpur in 1995 but never registered the property. He constructed a house on the land, which was rented out until we moved in after his retirement. We have all essential documents like electricity bills, phone connections, and house tax receipts in his name. The original landowner’s wife is ready to legally transfer ownership without any financial transaction. How should we proceed with registering the property legally?