Make a list of all the onomatopoeic words you can think of. Think through the sounds made by animals, people, vehicles, inanimate objects and elements of nature like wind, fire and water. Don't limit yourself at this stage; you won't have to use all the words you think of.
Circle the words that stand out to you or that you especially enjoy. Think of a story or theme that can relate all of them.
Draft a poem that uses as many of the circled onomatopoeic words as you want to include. One approach is to create a cyclical storytelling rhythm where, for example, one line describes an event and the next line describes the sound something made as a result.
Edit your poem to cut out unnecessary words, even out the rhythm, and fix any grammar and spelling errors.