Great question, because the job evolved a lot the last few years!
18 years ago, nothing existed in the French law to set up rules for the profession.
I am a human osteopath before being an equine osteopath, but I was also a semi-professional rider for years, while I was studying.
I learned with other equine osteopaths as well as with vets.
Now there are schools to become equine osteopath that are regulated, usually in France it takes you 5 years to have a renown diploma.