Costway / steam mop

I received my steam mop and set it up. However, the white pad keeps coming off. There is a triangular piece of plastic that I tried to put on, but that only makes a scratching sound across the floor. The instructions aren't clear enough. How do you get that pad to stay on? The unit was received on January 11/2019 and all parts seem to fit together well. It's just that one problem with keeping the pad on. I see that you only sent one pad. Wasn't I supposed to receive 2?