If you don't think you are a sinner then you need to read a few passages from the Bible, we'll start from Romans Ch3 V10,23 "There is none righteous, no, not one, all have sinned" The Apostle John says in the first book of john Ch1 V8 "If we say that we have not sinned we decieve ourselves" So lets start with a little test and see if you have sinned.
- Have you ever been drunk? (Ephesians 5:18)
- Have you stolen something that wasn't yours? (Exodus 20:15)
- Have you lied? (Exodus 20:16)
- Have you had sex with someone other than your spouse, or entertained lustful thoughts in your mind? (Matthew 5:28)
- Have you paid all your taxes? (Romans 13:6-7)
- Have you lived your life in subjection to the government (i.e., obeyed the laws of the land)? (Romans 13:1-2)
- Have you hungered after (coveted) something that didn’t belong to you? (Exodus 20:17)
- Have you ever replaced a four letter vulgar word with the name of Jesus? (Exodus 20:7)
- Have you ever disobeyed or dishonored your parents? (Exodus 20:12)
- Have you murdered anyone, or even had harsh thoughts about someone? (Matthew 5:22)
- Have you ever used anything as an object of worship or veneration? (Exodus 20:4)
- Have you ever given allegiance to anything else over God in your life? (Exodus 20:3)
- Has any unwholesome word proceeded from your mouth? (Ephesians 4:29)
If you have answered yes to any of those then you are a sinner and fall short of God's grace and forgiveness. Those who turn away God’s offer of salvation purchased for them through Jesus’ death on the cross will stand before God on the day of judgment still in their sins, only to be judged, justly condemned and cast away from God’s presence forever in Hell (Romans 2:5, Revelation 20:15). You do not want to go there! And God doesn’t want you to go there either (1 Timothy 2:4). That is why Jesus died on the cross for you. He loves you (Romans 5:8)!
Believe that Jesus came Born through the Virgin Mary not just to fulfil biblical prophesy he also came to die a very bloody painful death for your sake his blood rained down from the cross to cleanse you of your sins, but it is only through him and belief in him that you can be forgiven. You have to believe that after 3 days he rose from death and ascended into heaven to be with the Lord our God. "If you confess with your mouth Jesus as Lord, and believe in your heart that God raised Him from the dead, you shall be saved" (Romans 10:9).
Now I would give you a prayer you could say but I believe that if you are to Repent, it must be sincere and so it would be better if you spoke from the heart.
I would also suggest that you read through the New Testament first because that way you will under Jesus and the Lord properly and also to make more sense of the Old Testament, the NT also teaches you how to be a Christian.
Thanks to http://www.alwaysbeready.com/