I agree with confining him to a smaller area, but one thing that I found that totally worked with Topher was big time praise. Each time he peed on the pee pad we hooted and hollered, told him he was a good boy over and over again and gave him a 'cookie' (treat). It only took a day or so for him to dial in that doing it on the pee pad was a good thing!! You can't take your eyes off your pup for those first few days while training cause you have to catch them while they're doing the right thing or they won't have a clue what you're getting excited about!
Topher is a riot now...if I miss the fact that he pees on the pad, he comes over to me all excited with this little dance he does...like he's telling me 'look what I did, mom!' and he waits for his cookie. They're pretty smart little things and LOVE to please!!