[FirstYorkie]

At first, I would treat him like you would a puppy.

Take him outside quite often and when he potties appropriately, give him yummy treats and loads of excited praise. Keep an eye on him at all times and hurry him outside if you catch him going inappropriately. If it were me, I'd contain him in a small non-carpeted area when I couldn't watch him - just until you feel like you can trust him, of course.