Due diligence + Draft + Submit
Due diligence: Do your research, chat with your team, potential renters, friends/family, your accountant, etc. Then begin to build out your mini business plan for how you'd like to execute the model into your business.
Draft: Draft your model by using your own goals/desires and/or take from the templates provided. Taking the time between the due diligence stage and drafting up your model is super important and a ton of fun. So don't rush.
Submit: When your model is tight, and you believe it's a good representation of how you're going to operate, you'll complete the tax ruling document and mail it to the ATO.