Sync iTunes music library to iPhone

My new car has Apple CarPlay. It easily plays music from Apple Music. I synced my iTunes library to my iphone but CarPlay doesn't find the files. When I synced the files, the transfer did not ask for a location (like Music) so I'm not sure where they reside on my iPhone. In any case, I've used up a considerable amount of storage on my iPhone if this doesn't work. Is there a way to delete the files? (too many questions in one post, I expect)