Try to explain John chapter 3 to this person in context of the whole book of John.
This is how Scott Hahn explains about being born again in his audio series “Our Fathers Plan”. (Listen to the first few minutes of this section of Our Fathers Plan where they explain about being born again in a way which is a lot better that I can)
In John chapter 1 you have Jesus being baptized, water and the spirit are both shown together during his baptism.
John chapter 1 also shows that those who are “born of God” receive a supernatural Power to become children of God.
In John chapter two, you have people believing in him by his signs, but he would not trust himself to them, their natural human belief was not enough. In John chapter three, John gives us an example of this with Nicodemus saying that he believes because of the signs, just like was mentioned in chapter two. But Jesus tells him that you must be born again with the water and spirit (Baptism as we saw in chapter 1) to enter the kingdom of God.
We see that the discourse with Nicodemus being about baptism. It is framed with baptism, in John chapter 1, and then right after Jesus talks with Nicodemus, in chapter 3 verse 22, it says Jesus went with his disciples baptizing. (the only time the bible says that Jesus was baptizing) The whole discourse with Nicodemus is sandwiched between baptism.
Jesus is teaching that we need God’s supernatural Power to become children of God, we can not do this with our natural reasoning, we receive this power through baptism when we are "born again, or “born of God”. And Jesus goes on to say that we need baptism, that is being born again, to enter the kingdom of God.
Here are the verses which point to this understanding of baptism in John chapter 3 -
John Chapter 1: 11-13
He came to what was his own, but his own people did not accept him.
But to those who did accept him he gave power to become children of God, to those who believe in his name, who were born not by natural generation nor by human choice nor by a man’s decision but of God.
John Chapter 2: 23 - 25
While he was in Jerusalem for the feast of Passover, many began to believe in his name when they saw the signs he was doing.
But Jesus would not trust himself to them because he knew them all, and did not need anyone to testify about human nature. He himself understood it well.
John Chapter 1: 29-33
The next day he saw Jesus coming toward him and said, "Behold, the Lamb of God, who takes away the sin of the world.
He is the one of whom I said, 'A man is coming after me who ranks ahead of me because he existed before me.'
I did not know him, but the reason why I came baptizing with water was that he might be made known to Israel."
John testified further, saying, "I saw the Spirit come down like a dove from the sky and remain upon him.
I did not know him, but the one who sent me to baptize with water told me, ‘On whomever you see the Spirit come down and remain, he is the one who will baptize with the Holy Spirit.’
John Chapter 3: 1-7
Now there was a Pharisee named Nicodemus, a ruler of the Jews.
He came to Jesus at night and said to him, "Rabbi, we know that you are a teacher who has come from God, for no one can do these signs that you are doing unless God is with him."
Jesus answered and said to him, "Amen, amen, I say to you, no one can see the kingdom of God without being born from above."
Nicodemus said to him, "How can a person once grown old be born again? Surely he cannot reenter his mother’s womb and be born again, can he?"
Jesus answered, "Amen, amen, I say to you, no one can enter the kingdom of God without being born of water and Spirit. What is born of flesh is flesh and what is born of spirit is spirit.
Do not be amazed that I told you, ‘You must be born from above.’