The app is separated into three modes. You can change them at the top in the navigation bar.
Compose songs and find chords for your songs. Tap in a bar or on a chord in the circle of fifths to start composing. Assign chords from the circle of fifths to a bar.
The circle of fifths will be displayed traditionally. The relative minor chords will be displayed. Chords of a key are not highlighted anymore. This mode is dedicated to learning plain scales. Read more about it.
The circle of fifths highlights the chords of a key. These chords build up a mode. A mode has an associated scale that is displayed in the staff. Accidentals are listed at the beginning, as they would be listed on a score of a song that is written in the selected mode. Read more about it.