God's Kingdom rule is primarily seen in His people ; here are two sections in Romans teaching a little on this:
Rom14:16 Let not then your good be evil spoken of:
17 For the kingdom of God is not meat and drink; but righteousness, and peace, and joy in the Holy Ghost.
18 For he that in these things serveth Christ is acceptable to God, and approved of men.
Rom15:11 And again, Praise the Lord, all ye Gentiles; and laud him, all ye people.
12 And again, Esaias saith, There shall be a root of Jesse, and he that shall rise to reign over the Gentiles; in him shall the Gentiles trust.
13 Now the God of hope fill you with all joy and peace in believing, that ye may abound in hope, through the power of the Holy Ghost.
14 And I myself also am persuaded of you, my brethren, that ye also are full of goodness, filled with all knowledge, able also to admonish one another.
15 Nevertheless, brethren, I have written the more boldly unto you in some sort, as putting you in mind, because of the grace that is given to me of God,
16 That I should be the minister of Jesus Christ to the Gentiles, ministering the gospel of God, that the offering up of the Gentiles might be acceptable, being sanctified by the Holy Ghost.
Notice, it is within us, or in our midst: The Spiritual nature of the rule starts with believers in the midst of the enemies of God. It started in the middle east, among the Jews, but is now going worldwide Mt.28:18-20. It started in this way, as Jesus taught:
Lk17:
20 And when he was demanded of the Pharisees, when the kingdom of God should come, he answered them and said, The kingdom of God cometh not with observation:
21 Neither shall they say, Lo here! or, lo there! for, behold, the kingdom of God is within you.
22 And he said unto the disciples, The days will come, when ye shall desire to see one of the days of the Son of man, and ye shall not see it.
23 And they shall say to you, See here; or, see there: go not after them, nor follow them.
24 For as the lightning, that lighteneth out of the one part under heaven, shineth unto the other part under heaven; so shall also the Son of man be in his day.
25 But first must he suffer many things, and be rejected of this generation.