Question re: kicking Ex out

My divorce will be final this week. I don't currently live in our family home, but it belongs to me. My ex deeded our home to me (it's paid off), so my son & I would have some stability and a place to live. So, I told him that he could continue to live there until our divorce was final, then I needed to move back into it for financial reasons (I'm temporarily renting a house). Now he's not showing any interest in moving out.

How do I go about evicting him? He doesn't pay any rent, and we have no agreement, other than the verbal one. Do I need to serve him with a notice & what kind? Will I need to call the police? He's already known for almost 3 months that he'd have to move, and I can't afford to give him much more time. We live in Montana, and I couldn't find any applicable laws that would apply to our situation.

I appreciate anyone's help and/or advice!
Tracy