Its like asking "where do i get inspiration?" and for there's no Tutorial our there to cover that important part for Music. Everyone has its own possibilities to get some inspiration like listening to other music, looking up to other artist, transcribing already existing pieces into the Genre you have grown up with or sometimes the melody that suddenly rings in your head. I won't ever ask anyone where to start with Music or Production.. i just do it, because i feel like doing it... that occurs extremeley often sometimes or ill hit a total wall and need a break of a few days, some weeks or even month.