Adding Notes in small fonts (variation for different verses)

Welcome.

Select note(s).
Right-click.
Note Properties - Tick "Small".

Probably easiest to add the small notes in a second Voice (qv Voices).
You may also want to shorten the stems depending upon the appearance that you want.

Now, if you mean textual notes (as opposed to musical notes) then that is also easy enough: enter note or lyric or whatever, select it all and go to the bottom, left of the screen and adjust the font size.