Greetings Heather, welcome to YorkieTalk
Yea, our guys are sorta hard to train, but I've had it pretty easy, in that I have two Adult Dogs, which help train my new Puppy Ichabod.
Yorkies are basically very tidy guys. They prefer not to potty where they live. When Ickey did it in the wrong place, I cleaned the area, de-scented it as well, then lay a couple tasty Treats close, where he started associating that place with "Living area" not "Potty Area".
It just so happens that I have a very secure back yard and a Doggy Door for my guys to access it. Ickey has learned that the "right" area for potty is very accessible (that being outside).