Go to the fourth instance and make a few changes there. Move the ending notes to different positions. Change a few note lengths. You should have your first melody up and running. Change the tempo from the default 120 to 180.
Most tunes sound nicer at a faster clip.
It's time to add an accompaniment. Place quarter notes and stick to the same note for a bar at a time. It's time to add the beat. While Cakewalk has a Drum View for adding rhythm tracks, even a plain sequencer lets you use the above method to get similar results. Play with the relative volumes of each track till you're satisfied with the results.