Your first step is contact Legal Aid and enquire about organising a family dispute resolution (FDR) conference with the other party. FDR is mediation designed to help parties reach agreement about care arrangements for kids (or other family matters, such as property settlement) and is mandatory before either party can commence court proceedings.
The idea is to develop a parenting plan that you both agree to and then, if you like, have it made into consent orders that will give it legal standing. If the parties can't reach agreement though, or either party fails to make a genuine effort to reach agreement, then the mediator will administer a s60i certificate enabling them to pursue proceedings in court.
But first and foremost, contact Legal Aid. Relationships Australia also offer an FDR service, as do most family law accredited practitioners, but Legal Aid is the most affordable.
Hope this helps.