Practice, feedback, and reading a lot of writing of the sort you want to emulate. The last point is subtle but important. After reading a trilogy by an author

Practice, feedback, and reading a lot of writing of the sort you want to emulate. The last point is subtle but important. After reading a trilogy by an author with a distinctive writing style I'll find myself unconsciously writing and even speaking in a voice similar to theirs. Publish even what's imperfect so you can get feedback. Oh, and short sentences are good: they're easy to understand!