It simply means total obedience to Christ and
a total repudiation of your former life as a sinning human being. It begins with immediate obedience to Christ's commandment to be baptized. And then it involves surrendering every aspect of your life to Christ, and forsaking that which is contrary to the teachings of Christ and His apostles. Here is a biblical example:
LUKE 19
8 And Zacchaeus stood, and said unto the Lord; Behold, Lord, the half of my goods I give to the poor; and if I have taken any thing from any man by false accusation, I restore him fourfold.
9 And Jesus said unto him, This day is salvation come to this house, forsomuch as he also is a son of Abraham.
10 For the Son of man is come to seek and to save that which was lost.
Zacchaeus was the chief tax collector and he had become rich through extortion. But when Christ invited Himself into his house, Zacchaeus believed on Him, received Him joyfully, and acknowledged Him as "Lord". Zacchaeus did not call Jesus "Master" (rabbi) but "Lord" (Kurios). And because of that, he genuinely repented and declared his repentance through a serious commitment to make proper restitution.
He immediately gave away half his wealth to the poor! And even though a thief was required to pay double of what he had stolen (Exod 22:7), Zacchaeus pledged to restore four time what he had stolen. He was applying this principle to his restitution:
If a man shall steal an ox, or a sheep, and kill it, or sell it; he shall restore five oxen for an ox, and four sheep for a sheep. (Exod 22:1)
And because of his repentance and his acknowledging of Jesus as "Lord", Christ declared that salvation had come to this house. Also, the repentant thief on the cross addressed Jesus as "Lord".