As Lord, Christ is also head of the Church, which is his Body. Taken up to heaven and glorified after he had thus fully accomplished his mission, Christ dwells on earth in his Church. The redemption is the source of the authority that Christ, by virtue of the Holy Spirit, exercises over the Church. "The kingdom of Christ (is) already present in mystery", "on earth, the seed and the beginning of the kingdom".
Source: Catechism of the Catholic Church (Vatican.va)