The laws of eviction are different in different states. However, there are four basic steps in eviction.
1. The notice to vacate
2. Filing the Suit
3. Going to Court
4. Writ of Possession
You should first give notice of eviction according to the law in your state and then you can legally get them out.

 tusc. County real estate investorsi don;t know what state you live in but in ohio you must first post a 3 day notice for payment or to leave the premise . If they don't pay, then you can start the eviction process. You might want to join your local landlord's association. They can help you with all of this. To join you might have to pay dues but they are not much and you can claim this expense on your taxes. I have added a link to my assoc.