I've never really used it since I never had a song I liked and couldn't find by just typing its lyrics on YouTube
but Shazam and other music finders apps shouldn't be hard to figure out.
I'm not sure how it exactly works, but I assume it has an algorithm that identifies songs based on the lyrics and the music.
Anyway, if you're too lazy to Google a guide on how to use it, then maybe watch the video below and follow the steps carefully