In search engine, search including the "MIDI" keyword.
After you download the MIDI file, select [Open...] button and select [MIDI Score] app, the downloaded file is stored in the [Songs] tab.
In iTunes, select [Devices>App>File Sharing]. Drag and drop MIDI files to [MIDI Score]'s document.
Kill the [MIDI Score] app by pressing the home button twice. After that, open the [MIDI Score], new files are stored in the [Songs] tab.