How can I tranpose the song or parts?
Notation products' Staff menu offers two commands: (1) Transpose Actual Pitches and (2) Transpose Instrument Key. The first command transposes all of pitches up or down-- both what you hear and what you see.
The second command (Transpose Instrument Key) transposes the staff for individual instruments to their native keys. For example, for a B-flat clarinet, the Transpose Instrument Key command will transpose the notes in the part up two half-steps, so that a 'C' read in the B-flat clarinet's part actually is heard as a B-flat.
For more details, use the Help/User's Guide menu. Click the Index tab, and type in "transpose". Alternatively you can view a tutorial video on Transpositions at https://www.notation.com/TutorialVideos.php