You could start with finding a fitness instructor in your area and asking if you would be able to shadow them for a few training sessions. If you can, I would try to find at least 2 different trainers to follow a few times. This will give you a better idea of what being an insturctor entails.
It would be good to actually hire a trainer for a fitness assessment and a few sessions as well.
I do teach Fitness Instructor courses and CECs, but I teach them in Hawaii. Though I will travel to a site that wants a workshop or seminar.
If you are a beginner in the industry, I would also look into one more option. The YMCA is a good place to start you fitness career and they do offer their own certification if you need it. In the meantime while you’re gaining experience you can go for other certifications like ACE, NSCA-PT, etc. They are family and community oriented, something that I believe it’s a great place to start from. Once you have enough experience, branching out to bigger and more commercial gyms would be the next step (unless you like the environment at the Y). The Y will also help you get that first certification (it can be either on strength training or group fitness instructor) and having them as part of your resume is a great asset as well.
Do you mean for personal training, or for group exercise, or for something else?
Here is a link for a tool that lets you compare personal training certifications, if that is what you are looking for. If you can identify the best certification for your needs you can then find the training that meets the needs for that credential.