Hi,
It sounds like you want to change the Enharmonic Spelling of the note (eg. F# to Gb).
To change the enharmonic spelling of a note, you can:
1. click on the note to select it,
2. then press the "E" key on your keyboard (for "E"nharmonic) and press the Up or Down arrow key to show the notation as you want it.
Enjoy

Sherry