1. learn the basic three tone chords in the key of C (there are seven of them)
2. start picking out the melodies to well known simple folk songs by ear, christmas tunes (when johnny comes marching home again, i wish you a merry christmas, etc.)
3. figure out by ear the correct chords to go to those songs. the "most logical sounding chords" to fit the melody
4. play along with recordings of simple pop tunes and try to imitate the keyboard part. styles of music that are heavy on accordion/piano include polkas, south american vallenatos and cumbias, and mexican mariachi music.