A better suggestion: read more English literature, until you find a phrase that confuses you. Suspect it to be an idiom or something similar, THEN look it up.
"Don't put the cart before the horse" as we say. ;)
You can always search for English idioms in books or online, but you'll only get a very vague idea of how and when to use it. It's one thing to know an idiom, but another thing to know how to use it. Good luck!