The word of God is found in the Bible. To answer the question “What must we do” I’ll let His word speak for itself:
For all have sinned and fall short of the glory of God.
For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord.
Jesus answered him, “Truly, truly, I say to you, unless one is born again he cannot see the kingdom of God.”
Jesus said to him, I am the way, and the truth, and the life. No one comes to the father except through me.
because, if you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved. For with the heart one believes and is justified, and with the mouth one confesses and is saved. For the Scripture says, “Everyone who believes in him will not be put to shame.”
2 Corinthians 5:15
and he died for all, that those who live might no longer live for themselves but for him who for their sake died and was raised.
Behold, I stand at the door and knock. If anyone hears my voice and opens the door, I will come in to him and eat with him, and he with me.