Just play it!

Start on the inner row in the right and the upper four buttons
on the left.

Honk out some 3-chord melodies that you know well. The
'1' and '5' notes, where the melodies likely begin, are
on the 'press' two buttons apart.

On the left hand, five minutes experimentation will show
you the I, V, and IV chords 'oom' and 'pah' bits.

The instrument is made to be played intuitively by untrained
musicians. If' you're a trained musician, it will be even quicker
to fit the things you already know into the layout of buttons.

Once you've gotten the hang of that inner row for basic stuff,
you can move on to the outer row, which handles the chordal
structure of tunes a bit differently.

Don't 'overblow' the thing--- you need less air than you think.