After inspecting the vampire lord perks tree, your training continues. There is much to learn, but if you master the powers of the Vampire Lord, few enemies will be able to stand against you.

Select your powers from the Favorites menu.

Vampiric powers that are available to you can include abilities such as Vampire's Servant which lets you reanimate a dead corpse to fight for you, Vampire's Sight that lets you see in the dark (night vision), and Vampiric Drain that absorbs points of health from the target.

A very cool power is the BATS power, that lets you transform into bats and teleport a short distance in front of you.

Slaying mortal men with your life drains grants you new night powers and blood magic. Lord Harkon keeps a stable of thralls in the castle should you need to feed like the baser vampires to stave off the sun. Harkon says that this is all he has to teach you. If you wish to be reminded of these lessons, you can just ask him again.

You can ask him what you need to know about being a vampire. Harkon says that as a vampire, you will gain new powers, but also a weakness to sunlight. With each passing day that you do not feed, that weakness will become more deadly, but your powers will also become stronger. Feed upon those who are sleeping, and your vulnerability to sunlight will diminish along with your powers.

Ask him to tell you again about being a Vampire Lord. He says that when you first transform into a Vampire Lord, you will hover in the air. While you do, you will command the powers of Blood and Night. Descend to the ground, and you can attack with your claws and feed upon your prey to regain your strength. With experience, your powers will grow and you will discover new ways to use them.

If you check your quest log, you will find it has updated as follows:

When I brought Serana back home after freeing her from Dimhollow Crypt, her father, a powerful vampire lord,  offered me the gift of his blood I accepted the gift and joined his court

To complete the Bloodline quest, speak to Harkon again and accept his task.