The Standard Input type is used for editing notes by default. It allows you to add notes by toggling their pitches in the Pitches palette.
Select Standard in the popover from the Input type button to activate Standard Input and display Pitches palette in the Actions Tools panel.
First tap on the Pitch button adds corresponding note to the staff, the second tap - removes it. You can scroll the palette to see pitches with octaves lower or higher.
To change note on the staff to its enharmonic equivalent long press the Pitch button and select note in the Enharmonic equivalents popover.