Start by explaining what you'd need to do to get ramped up. What information would you need? What parts of the company would you need to familiarize yourself with? What other employees would you want to sit down with? Next, choose a couple of areas where you think you can make meaningful contributions right away. (e.g., "I think a great starter project would be diving into your email marketing campaigns and setting up a tracking system for them.") Sure, if you get the job, you (or your new employer) might decide there's a better starting place, but having an answer prepared will show the interviewer where you can add immediate impact-and that you're excited to get started.