First, it is asking you to consider how Augustine provides a way of finding a 'spiritual meaning' behind scripture that, at times, might even be in contradiction with its literal meaning.
We have seen this before, in Paul's letter to the Galatians, where he cites the story of Abraham and Isaac from Genesis. Because God asked Abraham to break the law and kill his son, Isaac, this story, Paul claims, is really about the importance of faith over law. That is, Paul finds a 'spiritual meaning' here that he then uses to reject all of the literal laws that are presented in the other books of the Torah (in particular, the law about circumcision). For Paul, this method of looking for 'spiritual meaning' beyond the literal meaning of the scripture is important because it will help him found this new belief in Jesus, which will eventually become Christianity. He is using it to set up a new 'religion' of sorts.
Augustine uses a similar method. But he is not so much interested in creating a new religion; he already has a religion (Roman Catholicism). Rather, when he looks for the 'spiritual meaning' of the scriptures, it is to help him interpret his own life story and to give meaning to that life. This is something that Paul is really not interested in.
And that brings us to the second and more important part of the question, which is how does Augustine deploy this method of reading to use his own life as 'proof' of the scriptures? The question uses the term 'Performative exegesis' which you might also take to mean a 'living interpretation' i.e. the way in which Augustine creates a narrative about his life that seems to confirm the teaching of the scripture. Or, to put it another way, the way in which Augustine uses scripture to narrate the key events of his life to show how he came to align his own will with that of God's.
This is what the question is really asking you about: how does Augustine do this? what examples from the scriptures does he use and for what purpose?
In answering this, I would really advise you to focus on one or two examples. Augustine is a very careful writer and there is a lot of stuff going on. We want you to take your time, look carefully at how he constructs a certain scene and what role scripture plays in that. To do this, you need to focus on only one or two examples and slowly reconstruct and analyze it/them.
You might also want to reflect on what his possible motivation for writing Confessions was and how his style - autobiography interpreted through the scriptures - helps/hurts that goal.
If it helps you to clarify what you think Augustine is doing, you can include a brief paragraph where you compare and contrast him to Paul (who also looks for 'spiritual meaning' in texts and whose biography is also important for his religious message).
But the essay should be about Augustine, not Paul. So only bring in Paul if you feel it will help clarify and develop your reading of Augustine.