pioneer ddj 400 Rekordbox

Hi) can someone explain how to put my music in ddj400 i install rekordbox, verify, got my playlist there but the problem don't understand how to drag music in the controller i try the buttons at the top but it's doesn't help in headphones it's play tracks, i connect them so i can change the level of sound but nothing more than this can't understand where i make mistake please help someone))