If the lines of whatever you're reading go all the way to the end of the paper or screen, congratulations, you're reading prose. It's really that simple.
Prose is everything that's not poetry, which means you're reading prose right now.
now you are
Novels? Prose (for the most part). Newspapers? Prose. Your biology textbook? Prose. And if you ever find a biology textbook written in poetry, by all means, please send it our way.