He knows nothing about how to live the Christian life. He does not even know everything there is to know about his birth. He does not know about justification, reconciliation or propitiation. All this he will discover to his delight later in his spiritual life. For the moment all he knows is that he was lost without Christ and with confidence in Christ's death on the cross he owns a right relationship with God.
New birth is the crisis that launches a process.
The process is maturity in Christ. When parents bring a baby home from the hospital they are concerned with nourishment, not life. The baby received life at conception. They are not concerned with life but with development. It would be a tragedy if the baby still had a baby's body at five years of age.