Now that David's main rival for the throne is dead, the tribes of Israel come to David and agree that he's really been their true leader and the shepherd of Israel for some time. Thus, they crown him king, and David makes a covenant with them.
He's thirty years old, now, at the beginning of his official reign, and will reign for forty years.
He'll stay in Hebron for the next seven years, and then rule from Jerusalem for the next thirty-three.
Next, David leads an army to Jerusalem to fight the Jebusites, who are ruling the city. To their surprise, the Jebusites are defeated, and David takes Zion.
Apparently, the lame and the blind people of Jerusalem sided with the Jebusites, so David decides he hates them, and orders them attacked and prohibited from his house.
David builds up the city, making it his own, with the support of his trusty friend, God.
The King of Tyre sends cedar wood to David, helping him to build his palace.
Furthermore, he takes more wives and concubines, and many more children are born to him.
The Philistines attempt to attack Jerusalem, since they've heard that it's got a new king. David fortifies himself and his soldiers in their stronghold, while the Philistines amass out in the valley below.
David asks God if God will help him fight and defeat the Philistines. God says he'll prevail.
They handily defeat the Philistines, God acting like a "bursting flood" of vengeance.
The Philistines abandon their idols, which are captured by the Israelites.
This isn't the end though, and the Philistines try to attack again. God tells David to march behind the Philistine lines and face them opposite a bunch of balsam trees. When they hear the noise of marching in the tops of the balsam trees, they should interpret it as God's sign to strike—which they do, whipping the Philistines yet once more.