Dragon Age 2 How to get a dog?

Answer 1

if you have a dog sitting in your house go to hawke's abilities skill tree and find the summon icon, map it to your quickbar and summon dog.

Answer 2

The dog companion comes with the Dark Emporium dlc. If you bought a new copy of the game, then you will find a dlc code included next to the manual. In order to summon the dog, you activate the Mabari Hound skill under the sustained skills menu.