For existing scores, those Style options are indeed the way to go. You've probably also want to change the various other text styles (for titles, tempo, rehearsal marks, etc) in Format / Style / Text Styles.
For new scores, you can do all of this very simply by selecting one of the Jazz templates when you create your score.
Comments
Use menu item: Format > Style > Score and select MuseJazz for 'Musical symbols font' and 'Musical text font'.
For existing scores, those Style options are indeed the way to go. You've probably also want to change the various other text styles (for titles, tempo, rehearsal marks, etc) in Format / Style / Text Styles.
For new scores, you can do all of this very simply by selecting one of the Jazz templates when you create your score.