How can christians go to heaven?

Answer 1

In theory Christians go to heaven after they die. Obviously their bodies don't go to heaven, but their immaterial spiritual essence or soul is thought to go. So far we do not have any concrete evidence of this, however. So it is a matter of faith.

Answer 2

Christians believe that one day God will judge all people, the living and the dead. During this judgment God's wrath will be on all unrighteous and ungodly people.

All people are separated from God by sin, this is a result of the disobedience of the first man and woman. Because of sin everybody deserves to die.

But God came to earth in the form of the man Jesus and He died in place of you and I. Now, God says if you want to escape judgment, believe that He died for you and you will be saved from judgment

After the living and the dead are judged some will go to everlasting life (heaven) some will go to everlasting death.

To go go to everlasting life believe Jesus died in your place:

John 3:16 For God loved the world so much that he gave his only Son, so that everyone who believes in him may not die but have eternal life.