Sierra will ask you to deliver at least 30 bottles of Quantum Nuka-Cola, so she'll be able to fill her fridge. You can agree to take a full Nuka-Cola tour (you would be rewarded with an ice cold Nuka-Cola) or if you're skilled enough you can convince Sierra to focus on explaining your assignment (screen).
Locate Sierra Petrovita's house once you've arrived at your destination. The village is located to the south-west of Smith Casey's garage. In order to activate this quest you must visit a very small village which goes by the name of Girdershade. Solution: I would recommend that you start this objective soon after you've left Vault 101 and visited Megaton, because your job will be to collect certain items and you'll want to 'unload' them from time to time.
