Since "explication" means a detailed analysis, you'd essentially select one element of the story and take it apart to explain how it works for and in the story. Start by reading the story and paying attention to what interests you. Are you intrigued by the dialogue? By the setting? By the character development? Choose the one that interests you most, then go back through the story methodically and take notes on every small detail related to the element you selected. Note it, explain it, and tell how it contributes to the quality of the story. For example, if you were analyzing the dialogue, you'd look at the rhythm, the vocabulary, what is said and unsaid, how the lines spoken by one character lead into those spoken by the other(s), and so on.