You can make the note names visible on the fretboard. Switching between sharp and flat is setting that you can toggle back and forth. The Display Notes shows all note names in the working range (here Fret 0 to Fret 14). The names will be under the circle that appears when a note is painted in.

A tick mark will be shown on the menu as a reminder which choice you made - default is "Sharp".

This is the picture for the "Sharp" setting.

This is the picture for the "Flat" setting.