Two avenues - ADFA or Direct Entry. Whether or not you have (or desire) a university degree is irrelevent. From mid to late high school develop a keen interest in aviation and the ADF. Study well at school and study the right subjects. Don't listen to people who say it's too hard or you won't get in. Speak to the real people doing to job (get numbers through recruiting/cadets/contacts). Finally just do it - get to recruiting and do the tests and interviews when you are at the right age or have finished school.
All the best.