The main things is to stick to the question and focus on one aspect. If you have done a devised piece and knew all the reasons behind your artistic choices this question should not be a problem. Let's say you choose to talk about the costumes of the characters. You have to think about what the costumes give to the piece and to the characters.Introduction - say you will talk about costumes and outline a brief plan of which costumes you will talk about. You can have a couple of paragraphs with information about the general idea behind the costume choices. This will show that you had an overall plan of what the costumes wanted to convey.Then have a couple of paragraphs that talk about specific characters in your devised piece and go in detail as to why the characters had these costumes.Things to consider when talkig about costumes - What do they try to convey?Time of the pieceColours could suggest an emotionTears or rips could convey some sort of actionThese are examples of things that you need to talk about to make sure you answer the question in detail and justify every directoria choice you had about the costumes.