Hi Leah,
There is more than just a few verse to explain about the Kingdom. It starts at the beginning when Adam lost dominion of the earth to Satan. Satan is the ruler of the earth, He is the prince of the power of the air. (Eph. 2:1-2) The LORD calls out Abraham to be a seed to which the promise of a redeemer (Gen. 3:15) would come. His promise to Abraham and His creation was that He would make of thee a great nation and a blessing to all the families of the earth.(Gen. 12:1-3). He Confirms it again to Isaac his son after Abraham's death. (Gen. 26:1-5). And He confirms it again to Jacob (Isaac's son) (Gen. 28:13-15; 35:11-12). After the Hebrews wind up in slavery to Egypt. (Book of Exodus) The LORD rescues them out of Egypt and they march around in the desert for 40 years because of unbelief. (Heb. 3:16-19) Israel is a Theocracy under God's direction and will. After 40 years Joshua was anointed by God to be Shepard of Israel. After Joshua God made them Judges. All this I'am writing is explained in Acts chapter 7. Israel was led by Judges for about 400 years. Samuel was the last Judge of Israel for they decided they wanted a King like other nations. Saul was the first king and was disobedient to the LORD's instructions. God rejected his leadership and David became King. God makes a Davidic Covenant with King David of Israel. The covenant is formed in 2 Sam.7: 5-19. It is a perpetual covenant. After King David the monarch was one mostly vile and disobedient. But The Davidic Covenant was still to be honored. (Ps. 89)
Christ Is The seed of the Son of David in the flesh and the Son of God with power in The Spirit.(Rom. 1:1-5) There are many more Scriptures, but you can find and study them. In Matthew His Genealogy starts with Son of David, for Matthew is the Gospel of Christ presented as the King of Israel (Son of David). So, what did Christ preach when He started His ministry? He took up where John The Baptist left off. (Matt. 3:1-17) (4:17; 23-25). From Matt. 5 thru Matt. 7:29 Jesus, The Son of David and The Son of God preaches the Constitution of the Kingdom of the Heavens.(Heavens is plural in the original script) There are 3 heavens in Scripture (2 Cor. 12:2). Understand, This is not the "Kingdom of God". It is in the Kingdom of God but not the Kingdom of God. The Kingdom of Heaven pertains to the Davidic Covenant God made with Israel. And the Christ preached that Gospel. It was not till after He was rejected as The Messiah (Matt. Chapter 12). It is then He begins to talk in parables of the mystery of the Kingdom of Heaven,(Matt. Chapter 13) And how it will be till He returns. After that he does not preach the Kingdom of Heaven again, but begins to prepare the apostles for His crucifixion. For the Kingdom of God. That is what is called the Gospel of the Grace of God. So The nation of Israel and it's rightful heir are put off till some other time. In Acts Chapter 1, The risen Christ begins to tell them of things pertaining to the Kingdom of God. The Kingdom of God is where God's throne is. It also includes Israel, The Church, all angelic beings, and every person that has returned to the loving obedience of the Lord (on earth and in heaven) It includes all those from Adam until the end judgement of all those who belong to Christ.
He has risen and Christ is sitting on the throne of the right hand of God (Heb.12:2). and many saw Him as He ascended in to the clouds. He sent the Holy Spirit. He is King of kings and Lord of lords 1 Tim. 6:16. So many saw Him ascend to His Throne before they passed.
The Apostles preached "The Gospel of the Kingdom and the Grace of God in Jesus The Christ.
In Christ
Douglas Summers