Put him in either a play pen or a doggie fenced area attached to a wire crate (leaving the crate on the outside of the fenced area) attach a water bottle on the fence, give him toys and puppy kong and nylabone, and a wee-wee pad at the opposite end of the crate. (never ever run of the house) Take him out about every hour and walk him around the yard, play with him, roll a ball, anything to stimulate him. When he goes potty, praise him and say good potty, in your sweetest voice.
Even when he goes on the pad. Mine were trained this way and now are trained to go outside or on the wee-wee pad if I'm not home. I love this training method for the small guys and of course for me because I don't relish going outside in the rain and they don't either. Also when we travel and stay at a hotel/motel, I don't like going out last at night or early morning, and they use the pad.