One way is to start with a Prototype and set the MIDI file names to your own MIDI file. For example:
- Ctrl+B to search prototypes for HMM
- Double-click HMMPatternGeneratorOnMIDIFiles to make a copy of the prototype to edit
- On the right, you'll see a parameter field called: MIDIFileNames
- Select/erase the default MIDI file name ('homeshome.mid')
- Click the icon to the right of the field, and select your own MIDI file
- Tap the space bar to play