Your answer should firstly include the name of the play, the author and some details of its composure, such as the date it was written or the context it was written in. For example, "‘A Streetcar Named Desire’ is a play by Tennessee Williams which was written in 1947 and has an opening scene which effectively helps to foreshadow and build up to key events and themes in the play." You should then go on to briefly summarise the opening scene and describe how it adds to the theme you wish to discuss. For example, I would argue that Blanche drinking in the opening scene helps to introduce the theme of alcoholism and escapism as we see Blanche use alcohol consistently throughout the play. You should then have roughly 3 to 4 main body paragraphs which help to justify your point made in the introduction, mine would be 1) the opening scene itself as an introduction to Blanche's personality, 2) the opening scene in reference to the beginning of her alcoholism, 3) Blanche's frequent lies to mask her alcoholism, and 4) the climax of the play in which Blanche's alcoholic tendencies lead to her demise. I would then conclude the essay by summarising my key points and linking them back to the question.