Essentially you need to develop the skill of writing, well atleast that’s what NESA wants you to.
The only way to prepare for this is to keep doing practice questions and check your answers with a teacher or with the sample response.
Once you do enough of them, the exam will like just another set of practice questions you did at home.
In addition to the above, ensure you have a thorough knowledge of literary techniques and their effects within a particular stimulus. The ability to correctly identify techniques is important and will allow you (in addition to practice) to write good quality responses.