There’s not set procedure for this but you should be aware that the Council is very unlikely to give you a DA without strata approval. Also there are aspects of the changes to common property that require Owners Corp approval and their support in the passing of by-laws.
So, in short, the place to start is with the Executive Committee and/or the strata manager, with a broadstroke plan of what you want to do.
What you then need to establish is which bits of the plan require OC and Council approval, and which merely need to be notified. At this point is is also worth talking to council about the DAs they might require.
Once you have established which parts require Special resolution by-laws, if any, you should talk to the EC to make sure they are generally on-side and then talk to a strata lawyer about drawing up the necessary by-laws.
At some point you should also talk to the EC about a work schedule, the delivery of materials and the removal of rubbish to minimise the disruption to other residents.
Finally, put together your whole package, hopefully with EC support, and present it to an EGM for approval. Don’t forget, the Owners Corp doesn’t have to allow you to change common property so you need your neighbours on-side from the start.