If you want to take the exam, you can consult in your junior and senior years. Different regions have different policies. In some places, you can take the exam in junior year, and in some places, you have to take the exam in senior year. Some even require you to get an undergraduate certificate.
The rule of taking the psychological counselor exam is that you must have a bachelor's degree or how long you have worked in the relevant place.
Whether to sign up for class or not depends on the place. Some places must go through training institutions, and some places can apply directly.