“But to as many as did receive and welcome Him, He gave the authority (power, privilege, right) to become the children of God, that is, to those who believe in (adhere to, trust in, and rely on) His name—Who owe their birth neither to bloods nor to the will of the flesh [that of physical impulse] nor to the will of man [that of a natural father], but to God. [They are born of God!]” (John 1:12-13, AMP).
What do you have to do to be called a child of God? Just believe that Jesus is Who He says He is and that He can do everything He says He can do. The pious things you do, the amount of knowledge you have and where you come from aren’t important. The only thing that matters is that you welcome Jesus into your heart. When you do, you are officially God’s child.