doppel always stores two beats. When you first turn on doppel your low beat will begin automatically.
To switch to your high beat: double tap your doppel anywhere on the face.
To switch back to your low beat: sweep your thumb back and forth over the ridge on doppel’s face three times.
If you want to change the tempo of your high or low beats, use the app to send another one of your saved rhythms. This will replace the rhythm currently stored on your doppel.