Then all Israel went to David at Hebron and told him, "We are all members of your family.
For a long time, even while Saul was our king, you were the one who really led Israel. And the LORD your God has told you, 'You will be the shepherd of my people Israel. You will be their leader.'"
So there at Hebron David made a covenant with the leaders of Israel before the LORD. They anointed him king of Israel, just as the LORD had promised through Samuel.
Then David and all Israel went to Jerusalem (or Jebus, as it used to be called), where the Jebusites, original inhabitants of the land, lived.
The people of Jebus said to David, "You will never get in here!" But David captured the fortress of Zion, now called the City of David.
David had said to his troops, "Whoever leads the attack against the Jebusites will become the commander of my armies!" And Joab, the son of David's sister Zeruiah, led the attack, so he became the commander of David's armies.
David made the fortress his home, and that is why it is called the City of David.
He extended the city from the Millo to the surrounding area, while Joab rebuilt the rest of Jerusalem.
References for 1 Chronicles 11:8
And David became more and more powerful, because the LORD Almighty was with him.
These are the leaders of David's mighty men. Together with all Israel, they determined to make David their king, just as the LORD had promised concerning Israel.