Hi there,
Rainbow is a cutie and what a loverly name. We was just the same with our dog Murphy when we got him.
It takes time for them to adjust, and in time she will learn.
We used to sit outside with Murphy for ages and when he did something we praised him to bits.
Also if there are any little mistakes at the very moment he did do anything in the house, we would pick him up and take him straight to the garden. Eventually it clicked.... all that is needed is time and little rainbow will learn.
Have fun with your new puppy, has they dont stay small for long.
Murphy's mum - Amanda