How does preaching the holy gospel open and close the kingdom of heaven?

According to the command of Christ: The kingdom of heaven is opened by proclaiming and publicly declaring to all believers, each and every one, that, as often as they accept the gospel promise in true faith, God, because of Christ's merit, truly forgives all their sins. The kingdom of heaven is closed, however, by proclaiming and publicly declaring to unbelievers and hypocrites that, as long as they do not repent, the wrath of God and eternal condemnation rest on them. God's judgment, both in this life and in the life to come, is based on this gospel testimony.¹