I’m a pastor so am very familiar with helping people who sin, but not very familiar with porn addiction. How can I best help someone who comes to me with this problem?

You know what you need to know to offer the person forgiveness. Do that as you would for any sin. But because of the nature of this addiction, it is highly recommended that you refer him or her to a good Christian counselor who specializes in porn addiction. This will offer the person the best chance for recovery from the addiction. But you will likely still need to be the primary individual there to help your member with day-to-day spiritual doubts and struggles.