I am my dad's power of attorney and he rents one of his houses to my aunt. They are always late paying rent and have destroyed the house. What can I do to get them out? My dad isn't until his right mind and they are taking advantage.

Do they have a written lease ?
Have you given them a bill for all the damage they have done and demanded payment?

But you give them written notice to evict and then if they do not move, take them to court

Since you have POA you can act for your father. You need to follow the law for evicting a tenant in your local area.