Keep him in an expen when you can't watch him. Cover the entire floor with peepads, and gradually over time (maybe every week) take up just one pad until you are down to just one pad.
When he is outside the expen, watch him LIKE A HAWK and take him to the pad every 30 minutes or so (he is veeery young, patience is key here) give him a keyword (potty or whatever you choose, but stick with that one word or phrase), and praise praise praise and more praise when he does it right!
Welcome to Yorkies they are wonderful!
We have a general training section here if you browse it you can find a lot of good advise about training your wee one
