How do I transfer/drop/drop a karaoke track from YouTube to garden shed app.

I am a newby and I would like someone to explain to me as one would to a five year old how I can do a vocal cover to a karaoke track I have located in YouTube in the GarageBand Appbank? The query was previously addressed but the statement there ‘Then drop the karaoke song into garageband. You do this by just draging and dropping the song file into garageband or if the song is in itunes just use garagebands media browser’ did not go into the detail of how one does that.