Training a Dog to Use a Piddle Pad?

I adopted 2 small dogs. One is a Chihuahua 7 years (Junior) and the other is a Chihuahua/Yorkie, 1 year old. Both are from different owners. I live in a small basement apartment. Any how, I was told they were both pee pad trained. However, I have had them a few days and am not sure which one used it, but it was only maybe 2 times. The rest of the time on they used my rug and go all over the apartment. Any suggestions on what to do?

By btrmomsy from Ontario, Canada