Jesus proclaimed very clearly that a born again experience is required for eternal life.

John 3:5  "Jesus answered, Verily, verily, I say unto thee, Except a man be born of the water and of the Spirit, he cannot enter into the kingdom of God."

Jesus went about doing good; healing the sick and all manner of good deeds.  Because the Pharisees, Saducees & chief religious persons of the day sought to kill him he could not clearly declare all of his doctrines.  Thus he taught in parables so that the Apostles could later teach others after his death.  Of the twelve Apostles, Simon Peter was the recognized leader.  Before his death, Jesus declared that Peter would be the one to reveal the keys of the kingdom of heaven.

Matthew 16:19 "And I will give unto thee the keys of the kingdom of heaven: and whatsoever thou shalt bind on earth shall be bound in heaven; and whatsoever thou shalt loose on earth shall be loosed in heaven."

After his resurrection, Jesus was seen of various individuals for about 40 days (Acts 1:3)  Jesus instructed them to go to Jerusalem where they would receive "power" that had been promised.  Then, he was received up out of their sight.

Acts 1:8  "But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth."

After they tarried there several days the Holy Ghost began to fall!  These individuals (about 120) were so affected by the out pouring of the Spirit they were mistaken for drunk people!  Peter stood up with the 12 Apostles and began to preach to them, declaring the history of Jesus Christ concerning his persecution and death.  Afterwards, the Jews were "pricked in their heart" and began to ask what they needed to do to make this right (ie. to be saved from these terrible deeds).  Peter answered clearly and concisely by using the keys that Jesus had given him earlier and declaring:

Acts 2:38  "Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost."

Repentance is simply changing the way an individual lives.  This is a challenging process to go through!  Real repentance will exhibit "godly sorrow".  There will be tears of regret and sorrow.  The individual must purpose to change their ways to comply with the Word of God.  Jesus preached repentance.

Luke 13:3  "I tell you, Nay; but, except ye repent, ye shall all likewise perish."

Once a person has repented of their sins they are ready for the born again process to begin.  To be born again of water an individual can simply obey Acts 2:38 (referenced above) by allowing a preacher to baptize them in water, by immersion, in the name of Jesus Christ.  The following scriptures demonstrate the necessity of water baptism in the name of Jesus.  

Acts2:38, Acts 8:35-39, Acts 10:47-48, Acts 19:3-5