You can find high quality horse trainers and horse training facilities all over the world and there are lots of them in the United States.
You can find full-service facilities that will have staff to exercise your horse, train your horse, and teach you how to properly ride your horse.
A facility like that will cost you more than a pretty penny, but you can also find facilities that will just provide a place to keep your horse and you can do all the work.
Those are much more inexpensive.
At the facility you choose, the staff must be experienced and capable.
There should be the veterinarians available at the training facility because in the training process there is a chance of the injuries to the horse.
The vet will also make sure that your horse gets its check ups.
Many horse training centers are even owned by veterinarians and many others are owned by experienced horse riders and trainers.
You can easily find horse training facilities in your area by searching online.
With a few minutes of searching you will be able to find many facilities and perhaps even find ratings and reviews of the facilities.
When you have a short list of facilities I recommend that you go visit them.
Meet the staff, tour the facility, meet the owners and ask as many questions as you can.
If you have a place to keep your horse (maybe at your horse) you can probably find a trainer that will come to your place to train your horse and teach you how to ride it.