If you have already asked Jesus Christ into your heart:
Even if you have previously prayed a prayer asking Jesus Christ into your heart, asking Jesus into your heart again is not wrong before God. I encourage you to say the following prayer and say it with meaning in your heart (sincerely or in your best effort). This will only strengthen you in Him because it demonstrates your commitment to the Lord. (That is your faith and heart's determination!)
There are three basic reasons people think they are saved but are not :
(1) They do not believe Jesus Christ is risen from the dead and is alive today: spirit, soul, and body.
(2) They have not confessed Jesus as Lord and Savior before man.
(3) The Word of God is clear in Mark 16:16, "He that believeth and is
baptized shall be saved ; but he that believeth not shall be damned."
So water baptism is a necessary "act of faith" in salvation.
We can lead you through the prayer part but you will need to confess Jesus Christ as Savior and Lord before another person. You will also need to find a Christian brother or sister in Christ who has been baptized, to baptize you.
Please Pray with me Now Focusing your heart's desire to be His Kingdom child!
Heavenly Father, I come to You now, I acknowledge You as God, creator of Heaven and Earth.
Heavenly Father I confess that I am a sinner. I have sinned against You.
I believe in my heart that Jesus Christ is Your Son and You sent Your Son to Earth, and that he was born of a virgin.
I believe that Jesus Christ is the One true sacrifice for my sins.
I believe that Jesus Christ was crucified on a cross as a sacrifice for the sins of the world, sins which have blinded me and separated me from You.
I believe, Heavenly Father, that You sent Jesus Christ to personally die for me.
I believe Jesus Christ, Your Son, took upon Himself all of my sins and the sins of all mankind.
I believe Jesus, who knew no sin, became sin for me that I may receive Eternal Life.
I believe Heavenly Father; You raised Jesus Christ from the dead and He is alive and well, seated at Your Right Hand in Heaven.
I now repent (turn) from my sins and choose to follow and obey Jesus Christ as my Lord and Savior. I ask You Jesus Christ to be the Lord of my life and to lead me in all areas of my life. Jesus Christ I receive You as my Lord and Savior with all my heart and believe that You are my King and My God.
Lord Jesus Christ, fill me with Your Holy Spirit, and use my life as a willing vessel. Heavenly Father, I ask that my life glorify You.

Thank You Heavenly Father for my salvation by faith in Jesus Christ and the Truth of Your Word,In Jesus' Name, Amen (so be it)!
For those who just can't seem to say that prayer, try saying this prayer first: "Heavenly Father, I come to You and ask You in Jesus' Name to set me free from any wrong thoughts, fear, doubt, unbelief, believing any lies, any lies of the enemy, the devil, or demonic spirits, any thoughts that I have that are hindering me now in coming to You. I ask You, Father God, to deliver me now of all hindrances to becoming Your born-again Kingdom child, in Jesus Christ's Holy Name. I resist the devil and all his demonic spirits must flee and leave my presence. Lord God, remove the lies and the hindrances and help me so I can say the above prayer of salvation in earnest from my heart! I ask You to force out, drive out, and bind all evil things far away from me, in Jesus' Name. Amen."
Now, go back and choose to say the prayer before this last one, with all of your heart, soul and being!
If you prayed the prayer asking Jesus Christ into your heart as your Savior and Lord, and you meant it, then you need to realize that the Living God, Creator of Heaven and Earth now lives within you! That is awesome! God is awesome!!!