There is more to it than you may think, but learning how to make your dog a service dog is a possibility. Most people purchase service dogs that are already trained, but some owners prefer to train a pet that they are already comfortable with. Read the full guide here: https://topdogtips.com/how-to-make-your-dog-a-service-dog/
Under the Americans with Disabilities Act (ADA), a service dog is defined as “a dog that is individually trained to do work or perform tasks for a person with a disability.” For the record, dogs are the only animal that can be considered a service animal according to the ADA.
"A great place to start is with online search. The internet has several lists of service dog trainers, but remember to do your research and make sure that they are what they appear to be. Just because they appear on a well-made website doesn’t mean they are qualified or even legitimate."