Certified nursing assistant courses have both classroom and clinical instruction components. While you may be able to complete the theoretical component through an online course, the hands-on clinical training must be conducted at a facility such as a nursing home or hospital. Even if you find a program that offers online courses for the theoretical portion of the class, you still have to be present for on-site clinical training in order to complete the course. You might want to choose a school in the state where you are stationed in next. The first step is to contact the school and ask which textbook they use for their CNA classes. Purchasing the book and studying when you have time will prepare you for the class as well as for the state exam.