Training program length, clinical requirements and testing procedures vary from state to state. You can find the exact requirements for your state by searching this website or you may ask here.
There are several ways to be trained as a nurse aide but to become certified you need to pass the nurse aide assessment examination. The most common way is to enroll and complete a nurse aide course provided mainly by two-year community colleges or specialized schools. Another way to become a nurse aide is to follow a training program at a long-term care facility or skilled nursing facility.
If you are a nursing student you may be allowed to skip training and just take the exams. The evaluation consists of two main parts: a written or oral exam and a hands-on, skills examination. A nurse aide candidate who passes both the written and the skills evaluation qualifies for obtaining a state nurse aide certification and is eligible for any entry-level nurse aide position.
You don't have to be a CNA to become a nurse but it may help if admission to the nursing program is competitive.