i've no idea how to start transcribing a song... should i just first heard the melody... and then the chords..? did you just use your ear and nothing else? it seems so intimidating...
just chart one element for now. whichever element you think you haven't mastered. if you haven't mastered rhythm, i recommend figuring that out first. just chart of the rhythm of the melody to every song you know, nothing else. if that's already a breeze for you then chart out the melody with notes. if that's already a breeze for you then chart out just the chords. if all these things are no problem, then chart out just the lyrics. if all these things are a breeze for you then get lost in the jungle for a few days and then when you come back start writing your own songs