The size of the music (notes, staves, etc) in Finale can be changed using the Page Layout tool. Perhaps the default music size looks too big or clumsy for the score you're writing. Other times, you may need to make the systems smaller before moving and rearranging the number of systems per page (very common).
To resize the music, under Page Layout menu, go to "Resize Staff System (system reduction)..."
In the "Resize Staff System" menu, you can resize...