Christ is in heaven and reigning over the church by His position of authority, in that He has been placed at the right hand of the Father. He is reigning over the church, functionally, by His Word and with His Spirit. He has sent us the Word of God and He has sent us the Spirit of God, and He is reigning through them.
Christ is also reigning by His benevolent leadership of giving. The Bible says, “He who descended is He who ascended and gave gifts to men” (Eph. 4:8–10). So, He reigns through giving Apostles. He gives men for leadership in the official places of the church. He gives women and their giftedness to the church. He gives people to the church. He gives ministries to the church: pastors, teachers, etc., and He gives gifts to every single member of the church. Everyone is gifted by the Holy Spirit with their spiritual gift. There are ministries Christ has established in His church and given to the church, and there are people that He has saved and given to the church. They were baptized and added to the church, so they are a part of the living stones that make up the New Testament temple of God. Through them, He’s ruling and reigning.
Further, as the head of His church, Christ sends His church as the embassy of the kingdom of God to extend the kingdom of God into the world. I also believe Christ is ruling and reigning over all the nations. He has bound the strong man, so now the focus is not simply on one covenanted nation, Israel, but on bringing in God’s covenant people from every tribe and nation. The King of kings, Jesus, is ruling and reigning through all of the nations.
There is much more that could be said, but for now, I’ll say that He is ruling and reigning not only as Creator and Redeemer in and through his church, but He is reigning as Sustainer by His providence. He is upholding all things by the word of His power. He is causing all things to work together for good to those who love God and are called according to His purpose. He is ordaining that the rain falls on the just and the unjust, which we call common grace.
Those are all ways to see Christ ruling and reigning. You could go even further and mention His intercessory work, but I would look at these things to see Christ as King in this now but not yet fulfillment of the kingdom.