Djay app

Hello all. I’m not a dj, just a teacher trying to create a song. We are having our yearly variety show and I’m the choreographer. I want to do a Beetlejuice mix. I can’t find what I’m looking for so I was trying to create my own. I downloaded the djay app but can’t figure out how to mix the songs together and record it. I’m using g four decks because I’m trying to work in several songs. Anyone know how this app works or where I can get instructions?