I Have A Yorkie That Is Paper Trained (easier For Mom Who Had A Stroke).?

I adopted a 5 -year old chihuahua/papillon mix today from the shelter, and I’ll get to bring her home Friday after she is spayed. She doesn’t appear to be housebroken, and I’m not sure if I should try to paper train her like the other dog or try to train her to go outside. Any suggestions? Also – any suggestions on helping the dogs become friends?