How do I teach my pup to pee outside?

I have a 1 year old Maltese puppy, (Febuary 28th 1 b-day hehe), and she just goes in our backyard to play with my 2 other dogs who are potty trained.She poops and pees in rooms. I have considered getting a trainer but I just dont have the time. Has anyone taught a 1 year old pup to potty?