there are many organizations through which you can become a personal trainer, and you can find that here at IDEA https://www.ideafit.com/fitness-certifications.
Which one to choose is the most frequently asked question, and I would look for one that is NCCA accredited and nationally recognized. My recommendations are usually for ACE, NASM and ACSM. I am somewhat partial to NASM. They have developed a model for training called OPT which is re-iterated in every of their specialty certifications and thus creates a coherent unit.
I’ve listed some well known ones here although there are likely hundreds in the country. It will take some considerations of several things to determine which one is right. http://spartatraining.com/blog/product-category/personal-trainers/person…