there may be other ways as well but here are the two main ones;
1) uni - go through the uni course (health sciences for ambulance studies) this is three years fulltime and your NOT garanteed a job.
2)diploma (like an apprenticeship) - apply for the diploma when they offer it (im not sure if they still are or if it is finished), if you are accepted you are then 'trained as you go' to a degree... you are given three months or so in a 'boot camp' then assigned to a station and put on the road, you then alternate between several months on the road and in the school room. you graduate as a paramedic, without the uni quals... worth noting that to become an ICP you will (may) then have to go to uni and do the course...
being a vollie will assist you in getting in, due to the work experience it provides, but it is in no way sure thing... also, getting into ambos is a damn site harder than MFS not necessarily on the fitness side of things, but in the maths/science/english/aptitude tests.