There are many people who think they cannot write, aren't good at writing, or don't know how to, but writing is for everyone. There are some people who have a gift of writing and it comes naturally to them, but for most people, writing is a work in progress. There are many different types of writing, styles, techniques, and voices.
There is much more than technical writing or the academic writing for courses in school. Writing can actually be fun and I've heard from people who study biology or math that writing is a fun stress reliever for them.
Creative writing, whether fiction or nonfiction, can take your writing somewhere you never thought possible. When you think of nonfiction, what do you think of? Biographies, memoirs, historical books? Well, there is a world of creative nonfiction you've yet to discover. For example, take "Jane, A Murder" by Maggie Nelson or "Motel Chronicles" by Sam Shepard. Both written poetically, they will inspire you to work harder and make you think about how you're describing what you're talking about. Nonfiction doesn't have to be some otherworldly fantasy; it can be a made-up story about the ordinary or a story with some nonfiction elements. Amy Hempel's novella "Tumble Home" and Lynda Barry's "Cruddy" will inspire you to learn how to mix humor with sadness and to write golden lines that leave readers thinking and questioning.
If you think you're not creative or are not interesting enough to write anything about yourself, think again. When I took creative nonfiction I thought, I'm boring. Why would my class be interested in a story about my life? But, as I worked on it, my class didn't think it was boring and eventually neither did I. In fact, my final piece for that class is one I still think of adding to and something that was incredibly therapeutic for me. I started writing about one thing, but the piece took me to different parts of myself that I could think about and explore.
Fiction and poetry are two other genres among many that can be therapeutic and help you discover things or simply better your writing. Although there are stories and poems about fantasy worlds or things that sound unique, find your own voice and style. You can write about your own experiences, something ordinary, or some wild world you create. Don't think about it too much and see where it takes you.
There's creativity in everyone and all it takes is some exploring to see what comes out of it. Writing is an incredibly powerful medium and the beautiful thing is anyone has the power to do it.