John 8.24 observes unless you believe that I am the Messiah, the Son of God, you will die in your sins.
God has come to earth as a man to live with men in order to reveal God to people and to reconcile people to Himself.
This is the simple message of Christianity: God has come to us.
If there is a God doesn’t it make sense that He would want us to know Him and to know specifically how we are to please Him?
God has come and revealed Himself to us in Jesus the God-Man and therefore requires all humanity to believe in Him alone by living as He instructed.
Jesus warned the religious leaders of His day that they were going to miss heaven because they refused to believe God was living among them. Many people saw the good deeds God did among them and resonated with His words so that they believed God was indeed in their midst thereby committing themselves to following Him.
What we believe about Jesus will determine where we spend our eternity.
Since God has come in Jesus He requires all humanity to recognize Him as God. How we live demonstrates our true belief. Those who live to please God are the true believers of God for they understand God is to be honored and obeyed and so change their behavior to reflect His reign over their lives.
Getting to heaven is quite simple really: it only requires believing God has come to earth in Jesus to restore us into a right relationship with God then living in such a way that we demonstrate we have been reconciled to God.
What is this way of living?
Loving God with all of our heart, soul, mind and strength and loving our neighbor as ourselves. Those who live this way reflect their belief that God has come and has reconciled them to Himself.