Learning to write sound, interesting, sometimes elegant prose is the work of a lifetime. The only way I know to do it is to read a vast deal of the best writing available, prose and poetry, with keen attention, and find a way to make use of this reading in one’s own writing.
The first step is to become a slow reader. No good writer is a fast reader, at least not of work with the standing of literature.
Writers perforce read differently from everyone else. Most people ask three questions of what they read: (1) What is being said? (2) Does it interest me? (3) Is it well constructed?
Writers also ask these questions, but two others along with them: (4) How did the author achieve the effects he has? And (5) What can I steal, properly camouflaged of course, from the best of what I am reading for my own writing? This can slow things down a good bit.