To answer this question, address the qualifications that are beneficial to the job. Focus on particular experiences and achievements which are related to the job of a salesman.
Show the interviewer how you can become a valuable asset to the store.
If you have done a job previously, you should mention what you have learned to apply in the new salesman job.
Put a focus on terms of customer service, selling techniques, and so on.
Point out the skills you have used to achieve your success in the previous job and demonstrate how such skills can be related to product sales.
For example, calmness under high pressure should be useful for a job as a salesman, too.