For this question, you can draw on past experience or present hypotheticals of how you will target new accounts if you get the job. What you really want to ensure, is that your answers show that you are able to think strategically about how to build your business.
If the company you are interviewing with is expanding into a new product line, discuss how you envision building that business specifically. Or, if the areas you are targeting for your own professional growth can be tied to a specific area of business, talk about how your growth is going to allow you to continue to bring on new accounts as you grow!