Very truly, I tell you, no one can see the kingdom of God unless they are born again.
How can someone be born when they are old? Nicodemus asked. Surely they cannot enter a second time into their mother's womb to be born!
Jesus answered: Very truly I tell you, no one can enter the kingdom of God unless they are born of wáter and the spirit.
John 3:3-6

Let's see another complementary text:
"In Gabaon the Lord appeared to Solomon in a dream at night and God said," Ask me whatever you want", replied Salomon ... Give to your servant a heart that know how to listen, to judge your people, to discern between good and evil " and God said .... I give you a wise and understanding heart " 1 Kings 3:9

This text reveals the meaning of "born from above ", "born again from the spirit".
Born from above is also known as "Gnosis", is to receive the Holy Spirit, in practical terms means to clean and renew our hearts , our thoughts and feelings, is asking a benevolent and peaceful heart towards the neighbor, to the other. With a renewed and cleaned heart we can see the world and the creation with the eye of the divinity and his intelligence : the spiritual gift of understanding, that is the reason that loves the good.
Receive the Holy Spirit is in other words repentance asking God for wisdom to reach the sacred listening and the eternal life or to say the knowledge of God, with the Holy Spirit we receive the superior spiritual gifts: the gift of wisdom, the gift of knowledge and the gift of discernment.
Recall another text : "Let the little children ... for theirs is the kingdom of heaven" Matthew 19
With a new heart we become new people and renewed . We all have a shadow, an unconscious full of conflicts and negatives aspects. Request and receive a heart that knows how to listen is to overcome and leave behind us our shadow for all the good who comes from the divinity , the spiritual gifts and perfections to resemble him and become his sons and also receive the ultimate prize: the immortality and the eternal life .
The sacrament of confirmation represents, symbolizes this "born from the spirit", the spirit "confirm" us in the teachings of the Gospel.