... By writing, like you said. It's no more complicated than that.

That you're asking this here leads me to believe there's some unknown (to me) internal resistance holding you back: start writing. Write some more. Then write some more.

You might be interested in books like "Bird by Bird" (Lamott) or "Do the Work" (Pressman) etc. (I've read BbyB a few times, and am re-reading/-listening to DtW again as I plow through some drudge work that's necessary, but irritating.)