You can enter the Melody mode from both Chords Mode and Table. Review Entering Melodies. When the mode change button displays "Melody" clicking on it will switch to Melody mode.

The important thing to know is that in Melody mode the status of the staff always reflects the melody note present on the big keyboard, not the melody note of the current chord.  Click on the current chord  to load the current chord's melody note into both the big keyboard and the staff.