In writing a brief paragraph using gerunds, you first have to be clear on what a gerund is and how they are used in a standard sentence. From a grammatical standpoint, gerunds may appear to be similar to past participles, but they are quite unique. Gerunds are based on verbs (so they signify an action or state of being), but they actually function as nouns in a sentence. Gerunds end in -ing, which should give you a clue as to how to identify and/or use them in a sentence. Gerunds can take the place of a subject (e.g., "Reading is one of my favorite activities"), or it can take the place of a direct object (e.g., "My daughter's favorite activity is reading").
Depending upon what aspect of Romeo and Juliet you are writing about, you need to think about how you can discuss the text using gerunds as part of your paragraph's sentence structure. You may want to consider the fighting that occurs in Act 1, Scene 1—this is a perfect opportunity to use gerunds to discuss the rivalry between the Montague and Capulet families using gerunds. You could also look at Romeo's questioning of love in Act 1, Scene 4, where he doubts whether love is truly a positive and worthwhile pursuit in life. Regardless of which scene or act you choose to write about, consider those -ing words when you structure the sentences in your paragraph.