Choose stories from a good children's Bible and read them with your child at regular times. As every parent knows, the same stories can be read multiple times to a child without boring the child. Children often ask for a particular story to be read over and over because some detail of the story appeals to them. Be patient with your child and indulge him with his favorites --- even if it seems, at first, that he is missing the main lesson. Deeper understanding will come in time.
Introduce simple concepts from your readings and discuss them with your child. Relate these concepts to your child's own life and to familiar things. For example, you can explain simply and clearly the idea that God is our Father; just as your child has a father, God is the Father of us all, or we are part of God's family, just as your child is part of a family.
Introduce Christian theology into the everyday life and activities of your child. Use Christian-themed activities, such as Christian crafts, Christian games or Christian coloring books, to reinforce readings and lessons. Make everyday situations "teaching moments" for your child, so that learning is a continuous process, rather than a separate part of a child's life.