myself and a friend from this forum google service dogs in my area. I emailed, then called a few. One very nice lady came out and tested my puppies. Most place will help you get into helping or even being a foster.
While 3 pups from my litter are trained service and therapy dogs, I've never dedicated the time to get my own certified. In truth, think Beau would be PERFECT, but the other two are not as laid back as he is.
From my understanding (could be wrong here), but believe it is a multi-step process. You have to complete your obedience training/certification. The dog has to be tested/certified for Canine Good Citizenship, then you advance to the training/certification for therapy or assistance.