Kay, some answers to your question for the exam are located here. You have to apply for the job online and register with the GA state employment career website, you will be able to find more details the more you poke around the website.
For juvenile probation, this is what they are looking for in GA.
Preferred Qualifications: Completion of a bachelor's degree at an accredited four-year college or university, with a major in the areas of psychology, sociology, criminal justice, social work, or education.
Exam & Evaluation Information: A written, multiple-choice test. Test subject areas: reading, interpreting, and applying procedural instructions and information from case studies.
In Atlanta, the written test for this job title is given every first and third Thursday of every month at 8:30 a.m. and 1:00 p.m. Because of limited seating, applicants are encouraged to arrive 30 minutes prior to the start of the session for check-in. Applicants should also apply for this job on-line, at this website, any time prior to the day of testing and bring their UserID (generated from the on-line application creation) and a picture ID to the test session.
Please note: Applicants will not be admitted once the test session has started. Please arrive 30 minutes prior to the start of the session for check-in.
Outside Atlanta, the test is given once a month on a Saturday on a ‘scheduled’ basis at regional testing centers (i.e., applicants are sent written notices providing date, time, and location of testing). To apply and request a regional test center location, applicants should complete the on-line application.