First of all......welcome to Pet Talk!!

I'm not sure it would be any different than house training a puppy. Except the fact that puppies "go" more often.
Just keep an eye on the dog at all times and take him/her outside as often as possible. Praise and treat when they potty where they are supposed to go. Do not punish when they go in the house.

There are more detailed things to do, but I'll let someone else get into those details.

Thank you for rescuing a dog. And we always love to see pictures here!!