Many experts don't believe that you should punish for making mistakes, just praise for correct actions. Punishment such as clapping your hands and a loud no, can get their attention, but often have consequences such as a fearful puppy, and building trust can take loads of time, and can go out of the window in a second, so that's why some experts so no punishment. Ignore the mistakes, and praise success. Also, not giving them a chance to make a mistake helps too. Crate training is effective because dogs don't like to mess their beds, and if the crate is the proper size, they will hold it for several hours rather than soil their bed. You then place them on the pad as soon as they are released from the crate, and praise the heck out of them when they do their business. Most people suggest confining them to the crate overnight, and an x-pen during the day where there are plenty of pads. I'm a little concerned about the leash, are you using it with a harness or collar; a collar can hurt their trachea. This link has a step by step guide for house breaking using either pads or the outdoor method.
Free House Training for Puppies and Adult Dogs - No More Accidents Starting Today!