To answer this question, you have to show the company how your skills can fit into the position, or in other words what is so special about you that's different than the other 20 people that they may interview for the position.
You have to get it in their mind that no one else will be able to bring to the table the skills that you have.
If the position requires a lot of attention to detail, customer service, etc, you talk about situations or experiences you've had in the past that correlates to those skills they're seeking. Then you wrap it up by saying this is why I'm the the perfect person for the position.