Congradulations, you've reached the point in Dragon Age 2 where you can start your first sidequest! Simply look on Gamlen's desk for the 'Bait and Switch' letter to start it. Thisvideo series will give you a full walkthrough of this important early quest that may even net you a new companion...
From the Creator:
1. Find the "Bait and Switch" quest by finding the letter on Gamlen's desk at Gamlen's house in Lowtown.
2. Locate and talk to Anso the Contact in Lowtown at night.
3. Travel to the Abandoned House in the Elven Alienage.
4. Fight your way through the Street Thugs and open the Smuggler's Cargo Chest.
5. Return outside and fight your way through the ambush.
6. Travel to Hightown at night and find Fenris. Don't forget to level him up once he joins your party.
7. Fight your way through Denarius's Manor, until you find the Magister's key at the far end of the first floor. Go upstairs and unlock the Magister's Chambers. An Arcane Horror will appear. Defeat it and exit the manor.