It starts with the Creation. God created a wonderful planet which operated perfectly (Genesis 1:31). God had fellowship with Adam and Eve (Genesis 2:8) in perfect love and harmony, however, there were rules they had to follow (Genesis 2:16-17).
With the deception of Satan under the disguise of a serpent, the human race fell (Genesis 3:1-7). With the fall of the human race, sin entered the whole world [not just people] (Genesis 3:17-19; Romans 5:12). The most devastating thing about the fall was our separation from God (Genesis 3:23). We became corrupt with sin, death is now on our lips, our deeds are evil and twisted, we seek darkness (Romans 3:10-18).
God created the human race for fellowship, but through our sins and transgressions, we earned nothing but eternal separation from God, the wages of our sin is death (Romans 6:23a).
God came onto the planet as a man named Jesus Christ (John 1:14); this was to set into motion His plan of redemption (John 3:14-15). Jesus was the incarnate God (Philippians 2:5-8), taught disciples to carry on His message of repentance from sins [that is, to change our mind about sin] (Luke 24:44-47) and set out to pay for our transgressions out of His love for us (Romans 5:15-17).
Jesus Christ died on the cross (John 10:22-29; 19:16-30). He rose from the dead to assure us He could raise us in the last days (Luke 24:1-12).
He kept us in the world to pass on the message of repentance from sins until He returns (Luke 24:46-47). We are not justified in any way by our sacrifices or good works (Ephesians 2:8-9), but on God’s own sovereign election (Romans 9:16).
Prior to genuine belief, He transforms your heart to give you a desire to follow Him in obedience (John 3:4-8, 2 Corinthians 3:18). Salvation comes when you believe Jesus is the Son of God who paid the sacrifice for our sins (John 1:12). When you truly believe [not in a casual sense, but a full sense], you will have a desire to renounce your sins and follow Him in obedience (1 John 5:1-4).
He promised to return to gather us to Him later (Matthew 24:29-31). All people will have a resurrection. Those that are His will practice His commands in obedience to Him, they will be returned to fellowship with God after a judgment period (Revelation 21:3), but those that refuse His commands, will be cast into the pit of fire where there is eternal separation from God (Revelation 20:15).
If you got those things down, find a good local church who is active in the community, sit under the teachings of the church, learn the doctrine of the church, and then get involved. The test of your salvation is your obedience to His word. No human person can give you assurance that you are saved, but the part of God called the Holy Spirit will confirm that in you.