Speak about your professional background. If you have experience in retail sales, provide dates and other details such as product range, number of customers per day or hour, size of outlet, etc. If you lack experience in this specific field, try to relate any experience you do have, even if volunteer, to the retail manager position. Find commonalities; relate some anecdotes that will show you can perform as a retail manager. Consult with friends involved in retail establishments for assistance if need be.