For download a midi file , you search in internet the music you want and you download it. There is a link for download classical pieces ( http://www.piano-midi.de ) but if you are on ios this is a probleme beacause its hard for download something on internet
Download it and import the song and normally he will have music (sorry for spelling mistakes i use google translate)
I don’t know HOW to download it.
I don’t have a midi file