Creation stories exist in most religions and cultures of the world. These stories do not just recount the steps of creation, but they also attempt to give meaning, explaining why the world and its different cultures are the way they are. Creation stories may be presented in a very simple manner, or they may be laden with symbolism and imagery. The creation story you write will be limited only by your imagination. It can take any form you choose.
Choose your story's focus. What matters most to you? What do you want to bring meaning to? Do you enjoy the natural world and observing how ecosystems work together to provide for all living beings? Are you fascinated by the development of human culture or the coexistence of humanity with nature? Are you interested in magic, religion or philosophy? Is there a problem your creation story could explain or explore? Whatever your interest, you can make that the focus of your creation story.
Research existing creation stories. Your story should be your own, not an amalgam of other legends, but reading other stories may give you a feel for the way creation stories address the "why" questions of life.
In the Judao-Christian creation story, for instance, the steps of creation are recounted as a seven-day process, the pinnacle of which is the creation of humanity on the sixth day, after which God rested. In "The Record of Ancient Things," a Japanese creation story, three deities direct lesser deities to solidify the island of Japan and eventually to dispatch the first ruler from the heavens to Japan.
Consider what brought your universe into existence. Are these forces purely scientific, and if so, how will you describe those forces in story format? Rather than science, perhaps you want one or more divine beings to be the agents of creation. If so, what are these beings' natures? Do they have consciousness? How do they relate to one another and to their creation? What was their motive in creating the universe?
Think about the physical nature of your universe. Will your story primarily deal with one planet or one area of that planet, or will it be more far-reaching? If you focus on one planet, are there nearby planets or moons that can be observed? Consider land masses, oceans and climate. Your creation story does not need to address all of these explicitly, but the more you know about the physical nature of your creation, the more interesting details you can provide.
Consider the nature of the living creatures in your universe, thinking about plants, sea life, flying creatures and land creatures. Give yourself permission to imagine exotic creatures and fantastic plants. How do they all fit into the environment? Do food chains --- who eats whom --- play a role in your story? Think about how the weather and geography affect your creatures.
Populate the world with at least one sentient --- intelligent and self-aware --- creature. How did your sentient creature come into being? Was this a special moment in the creation process, or was it a natural evolution, no different from the beginnings of plants and animals? Make notes about cultures and races. Is there a class system? How do the genders interact? If there is a divine being in your story, how do your sentient beings relate to the divine?
Write your creation story in one sitting if possible. Let the words flow freely, rising from all the research, planning, thinking and imagining that you have done. Do not worry about grammar or spelling at this point. Just get the words onto the page.
Re-read your story and ask yourself if it clearly addresses not only the events of creation but also the meaning, or why question, you chose as your focus. Check spelling and grammar. Review the story for consistency. Re-write sections if necessary. Share the story with a few trusted people, asking for their constructive criticism, and revise again if their feedback is helpful.
In each step, keep the "why" question before you. For example, it is not enough to say that the deities created unicorns. You must also say why the deities chose to do so.