What would be the best way to structure my introduction?

The introduction is a vital part of your writing, particularly considering it is the first impression the examiner will get of your essay. Firstly, it is important to state what you will be arguing for/discussing throughout your essay in the introduction, for example - say the question is to discuss whether or not the narrator is reliable or unreliable. Within your introduction you should clearly state whether you believe the narrator is reliable or not and then throughout the essay you argue for this point of view. 

Another suggestion of mine would be to signpost the topic sentences you will be discussing throughout the essay. For example, if your first paragraph is, say, focused on the 'helplessness of the female protagonist in the face of a patriarchal society', then it is important to mention in the introduction that this will be discussed throughout the essay. It also helps to signpost the topic sentences in the order they will be discussed throughout your paragraphs, as this aids in making sure the essay will be concise and easy to follow, as well as making it seem more organised.

Thirdly, I would suggest to use keywords from the essay question within the introduction - this helps to make sure you do not not stray from the topic of the question, as well as emphasising to the examiner that you are focusing on the right theme/character etc.