Additional training may be required.
A specific handler pairs with dog to test/work.(aka you)
Tests require dog to be still/calm, as people with medical equipment move around.
Among others.
A dog temperment test should be involved, also.
And health/vaccination requirements.
Therapy dogs have fewer rights to go everywhere. Unlike service dogs.
But are great for visiting seniors, as you mentioned.
A kind thought.
It's helpful to join an organization, for therapy dog handlers.
As dues often provide help, in case of legal issues. And great resource for questions/concerns.
Connects you to others with similar interests, for meet-ups, fun events, socializing.
Here is a good one, imo:
http://www.tdi-dog.org/
Website also lists test requirements.
Hope helps.