1. A King As the Ruling Head.

Matthew 21:4-5 Behold, thy King cometh unto thee…
Colossians 1:18 And he is the head of the body, the church: who is the beginning, the firstborn from the dead; that in all things he might have the preeminence.

2. A Throne From Which the King Issues Decrees.

Hebrews 1:8 But unto the Son he saith, Thy throne, O God, is for ever and ever: a sceptre of righteousness is the sceptre of thy kingdom.
Hebrews 4:16 Let us therefore come boldly unto the throne of grace…

3. Territory Over Which the King Has Jurisdiction.

Matthew 28:18 All power is given unto me in heaven and in earth.

4. Subjects In That Territory to Rule Over.

James 4:7 Submit yourselves therefore to God.
1 Peter 3:22 Who is gone into heaven, and is on the right hand of God; angels and authorities and powers being made subject unto him.

5. A Law to Govern the Subjects.

Hebrews 8:10 … I will put my laws into their mind, and write them in their hearts: and I will be to them a God, and they shall be to me a people:

Conclusion:

All of these essentials are present and working in this dispensation of grace. Jesus Christ is the King of heaven and earth and dwells with His people. He sits upon the throne and is the head over the church. His law of holiness is in the hearts of the saints and they are reigning in this life. Hence, the Kingdom of God has already been set up.